fix \N{ (named unicode characters) in strings being turned into f-strings

[DetachHead]

fixes #1501

tests failing (i think) because the client in the tests does not send a DidChangeTextDocument notification before sending the onTypeFormatting request. i have no idea if its guaranteed that clients will always send them in that order so i'm hesitant to update the tests to do that just because vscode does.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

sympy (https://github.com/sympy/sympy)
-     Type of "cg" is "Zero | ZeroArray | Unknown | Basic | ArrayContraction | PermuteDims | ArrayTensorProduct" (reportUnknownVariableType)
+     Type of "cg" is "PermuteDims | Basic | Unknown | Zero | ZeroArray | ArrayTensorProduct | ArrayContraction" (reportUnknownVariableType)
-     Type of "cg" is "Unknown | PermuteDims | Zero | ZeroArray | Basic | ArrayDiagonal" (reportUnknownVariableType)
+     Type of "cg" is "Unknown | PermuteDims | ArrayDiagonal | Zero | ZeroArray" (reportUnknownVariableType)
-   .../projects/sympy/sympy/printing/tests/test_str.py:994:16 - warning: Argument type is partially unknown
+   .../projects/sympy/sympy/printing/tests/test_str.py:994:16 - warning: Argument type is unknown
-     Argument corresponds to parameter "object" in function "__new__"
+     Argument corresponds to parameter "object" in function "__new__" (reportUnknownArgumentType)
-     Argument type is "Unknown" (reportUnknownArgumentType)
-     Type of "cg" is "Zero | ZeroArray | Unknown | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims" (reportUnknownVariableType)
+     Type of "cg" is "PermuteDims | Basic | Unknown | Zero | ZeroArray | ArrayTensorProduct | ArrayContraction" (reportUnknownVariableType)
-     Type of "cg" is "Zero | ZeroArray | Unknown | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims" (reportUnknownVariableType)
+     Type of "cg" is "Zero | ZeroArray | Unknown | Basic | PermuteDims" (reportUnknownVariableType)
-     Type of "cg" is "Zero | ZeroArray | Unknown | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims" (reportUnknownVariableType)
+     Type of "cg" is "Zero | ZeroArray | Unknown | Basic | PermuteDims" (reportUnknownVariableType)
-     Type of "cg" is "Unknown | Zero | ZeroArray | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims | ArrayAdd | ArrayDiagonal" (reportUnknownVariableType)
+     Type of "cg" is "Unknown | PermuteDims | ArrayDiagonal | Zero | ZeroArray" (reportUnknownVariableType)
-     Type of "cg" is "Zero | ZeroArray | Unknown | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims" (reportUnknownVariableType)
+     Type of "cg" is "PermuteDims | Basic | Unknown | Zero | ZeroArray | ArrayTensorProduct | ArrayContraction" (reportUnknownVariableType)
-     Type of "cg" is "Zero | ZeroArray | Unknown | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims" (reportUnknownVariableType)
+     Type of "cg" is "Zero | ZeroArray | Unknown | Basic | PermuteDims" (reportUnknownVariableType)
-     Type of "cg" is "Zero | ZeroArray | Unknown | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims" (reportUnknownVariableType)
+     Type of "cg" is "Zero | ZeroArray | Unknown | Basic | PermuteDims" (reportUnknownVariableType)
-     Type of "cg" is "Unknown | Zero | ZeroArray | ArrayTensorProduct | ArrayContraction | Basic | PermuteDims | ArrayAdd | ArrayDiagonal" (reportUnknownVariableType)
+     Type of "cg" is "Unknown | PermuteDims | ArrayDiagonal | Zero | ZeroArray" (reportUnknownVariableType)
-     Type of "approximants" is "(l: Unknown, X: Symbol = Symbol('x'), simplify: bool = False) -> Generator[Unknown | float, Any, None]" (reportUnknownVariableType)
+     Type of "approximants" is "(l: Unknown, X: Symbol = Symbol('x'), simplify: bool = False) -> Generator[Unknown | Expr | Any | ComplexInfinity | NaN | Rational | Zero | Infinity | NegativeInfinity | Float | float, Any, None]" (reportUnknownVariableType)
-     Type of "lcm" is "(f: Unknown, g: Unknown | None = None, ...) -> (Expr | Unknown | One | Poly | Any | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number)" (reportUnknownVariableType)
+     Type of "lcm" is "(f: Unknown, g: Unknown | None = None, ...) -> (Expr | Unknown | One | Poly | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number | Any)" (reportUnknownVariableType)
-   .../projects/sympy/sympy/series/approximants.py:14:5 - warning: Return type, "Generator[Unknown | float, Any, None]", is partially unknown (reportUnknownParameterType)
+   .../projects/sympy/sympy/series/approximants.py:14:5 - warning: Return type, "Generator[Unknown | Expr | Any | ComplexInfinity | NaN | Rational | Zero | Infinity | NegativeInfinity | Float | float, Any, None]", is partially unknown (reportUnknownParameterType)
-     Type of "c" is "Expr | Unknown | One | Poly | Any | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number" (reportUnknownVariableType)
+     Type of "c" is "Expr | Unknown | One | Poly | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number | Any" (reportUnknownVariableType)
-     Type of "c" is "Expr | Unknown | One | Poly | Any | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number" (reportUnknownVariableType)
+     Type of "c" is "Expr | Unknown | One | Poly | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number | Any" (reportUnknownVariableType)
+   .../projects/sympy/sympy/series/approximants.py:106:9 - warning: Type of "out" is partially unknown
+     Type of "out" is "Expr | Unknown | Any | ComplexInfinity | NaN | Rational | Zero | Infinity | NegativeInfinity | Float | float" (reportUnknownVariableType)
-     Argument type is "Generator[Expr | Unknown | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | _NotImplementedType | Poly | Any, None, None]" (reportUnknownArgumentType)
+     Argument type is "Generator[Expr | Unknown | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | Poly | Any, None, None]" (reportUnknownArgumentType)
-     Argument type is "Generator[Expr | Unknown | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | _NotImplementedType | Poly | Any, None, None]" (reportUnknownArgumentType)
+     Argument type is "Generator[Expr | Unknown | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Infinity | NegativeInfinity | Float | Poly | Any, None, None]" (reportUnknownArgumentType)
-   .../projects/sympy/sympy/series/approximants.py:109:24 - error: Argument of type "float" cannot be assigned to parameter "expr" of type "Basic" in function "simplify"
+   .../projects/sympy/sympy/series/approximants.py:109:24 - error: Argument of type "Expr | Unknown | Any | ComplexInfinity | NaN | Rational | Zero | Infinity | NegativeInfinity | Float | float" cannot be assigned to parameter "expr" of type "Basic" in function "simplify"
+     Type "Expr | Unknown | Any | ComplexInfinity | NaN | Rational | Zero | Infinity | NegativeInfinity | Float | float" is not assignable to type "Basic"
-     "float" is not assignable to "Basic" (reportArgumentType)
+       "float" is not assignable to "Basic" (reportArgumentType)
-     Type of "apart" is "(f: Unknown, x: Unknown | None = None, full: bool = False, **options: Unknown) -> (Unknown | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Expr | Poly)" (reportUnknownVariableType)
+     Type of "apart" is "(f: Unknown, x: Unknown | None = None, full: bool = False, **options: Unknown) -> Unknown" (reportUnknownVariableType)
-   .../projects/sympy/sympy/series/formal.py:116:13 - warning: Type of "terms" is partially unknown
+   .../projects/sympy/sympy/series/formal.py:116:13 - warning: Type of "terms" is unknown (reportUnknownVariableType)
-     Type of "terms" is "Unknown | One | NegativeOne | Zero | Integer | NaN | ComplexInfinity | Rational | Expr | Poly" (reportUnknownVariableType)
-   .../projects/sympy/sympy/series/formal.py:117:16 - warning: Type of "has" is partially unknown
+   .../projects/sympy/sympy/series/formal.py:117:16 - warning: Type of "has" is unknown (reportUnknownMemberType)
-   .../projects/sympy/sympy/series/formal.py:118:17 - warning: Type of "terms" is partially unknown
+   .../projects/sympy/sympy/series/formal.py:118:17 - warning: Type of "terms" is unknown (reportUnknownVariableType)
-     Type of "terms" is "ComplexInfinity | Expr | Integer | NaN | NegativeOne | One | Poly | Rational | Zero | Unknown" (reportUnknownVariableType)
-   .../projects/sympy/sympy/series/formal.py:118:25 - warning: Type of "doit" is partially unknown
+   .../projects/sympy/sympy/series/formal.py:118:25 - warning: Type of "doit" is unknown (reportUnknownMemberType)
+   .../projects/sympy/sympy/series/formal.py:120:36 - warning: Argument type is unknown
+     Argument corresponds to parameter "expr" in function "make_args" (reportUnknownArgumentType)
-     Type of "doit" is "Unknown | ((**hints: Unknown) -> One) | ((**hints: Unknown) -> NegativeOne) | ((**hints: Unknown) -> Zero) | ((**hints: Unknown) -> Integer) | ((**hints: Unknown) -> NaN) | ((**hints: Unknown) -> ComplexInfinity) | ((**hints: Unknown) -> Rational) | ((**hints: Unknown) -> Expr) | ((**hints: Unknown) -> Poly)" (reportUnknownMemberType)
-   .../projects/sympy/sympy/series/formal.py:120:36 - error: Argument of type "ComplexInfinity | Expr | Integer | NaN | NegativeOne | One | Poly | Rational | Zero | Unknown" cannot be assigned to parameter "expr" of type "Expr" in function "make_args"
-     Type "ComplexInfinity | Expr | Integer | NaN | NegativeOne | One | Poly | Rational | Zero | Unknown" is not assignable to type "Expr"
-       "Poly" is not assignable to "Expr" (reportArgumentType)
-     Type of "lcm" is "(f: Unknown, g: Unknown | None = None, ...) -> (Expr | Unknown | One | Poly | Any | Rational | NaN | ComplexInfinity | NegativeOne | Zero | Integer | Infinity | NegativeInfinity | Float | Number)" (reportUnknownVariableType)

... (truncated 3621 lines) ...