IDL4CSP — Resolution for name clashes with the Discriminator property name is invalid

The proposed conflict resolution rules for union members called Discriminator, which prepend an '@' in front of union member named Discriminator, are invalid. The '@' can only be applied to names that conflict with C# keywords (see https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/inside-a-program/identifier-names).

Add conflict resolution rules for conflicts with identifiers that are not C# keywords

Currently the specification only defines conflict resolution rules for names that conflict with C# keywords. This resolution introduces a rule to resolve conflicts with names that are not C# keywords.

The resolution also provides a valid solution to resolve name clashes with the property representing the union discriminator that is consistent with the IDL4 to Java Language Mapping.