Handle new warnings

Author: AArnott

test/Microsoft.VisualStudio.Threading.Tests/.editorconfig

@@ -0,0 +1,5 @@
+[*.cs]
+# xUnit1030: Test methods should not call ConfigureAwait(false)
+dotnet_diagnostic.xUnit1030.severity = none
+# xUnit1031: Test methods should not use blocking task operations
+dotnet_diagnostic.xUnit1031.severity = none