Properly escape constant regex patterns (#3299)

Fixes #3292

(cherry picked from commit d316b35)

Author: roji

src/EFCore.PG/Query/Internal/NpgsqlQuerySqlGenerator.cs

@@ -962,7 +962,7 @@ protected virtual Expression VisitRegexMatch(PgRegexMatchExpression expression)
         }
         else
         {
-            Sql.Append(constantPattern);
+            Sql.Append(constantPattern.Replace("'", "''"));
             Sql.Append("'");
         }
 

test/EFCore.PG.FunctionalTests/Query/NorthwindFunctionsQueryNpgsqlTest.cs

@@ -118,6 +118,23 @@ await AssertQuery(
 """);
     }
 
+    [Theory]
+    [MemberData(nameof(IsAsyncData))]
+    public async Task Regex_IsMatch_with_constant_pattern_properly_escaped(bool async)
+    {
+        await AssertQuery(
+            async,
+            cs => cs.Set<Customer>().Where(c => Regex.IsMatch(c.CompanyName, "^A';foo")),
+            assertEmpty: true);
+
+        AssertSql(
+            """
+SELECT c."CustomerID", c."Address", c."City", c."CompanyName", c."ContactName", c."ContactTitle", c."Country", c."Fax", c."Phone", c."PostalCode", c."Region"
+FROM "Customers" AS c
+WHERE c."CompanyName" ~ '(?p)^A'';foo'
+""");
+    }
+
     [Theory]
     [MemberData(nameof(IsAsyncData))]
     public async Task Regex_IsMatch_with_parameter_pattern(bool async)