Fix #333. Compilation fails when there are 2 generic union types with the same name: MyUnion<T> and MyUnion<T1, T2>.

[Dixin]

The following code cannot be compiled because of Result<T, TError> and Result<TError>:

[Union]
public partial record Result<T, TError>
{
    public partial record Ok(T Value);
    public partial record Error(TError Value);
}

[Union]
public partial record Result<TError>
{
    public partial record Ok();
    public partial record Error(TError Value);
}

public static class Result
{
    public static Result<T, TError> Ok<T, TError>(T value) => new Result<T, TError>.Ok(value);

    public static Result<T, TError> Error<T, TError>(TError value) => new Result<T, TError>.Error(value);

    public static Result<TError> Ok<TError>() => new Result<TError>.Ok();

    public static Result<TError> Error<TError>(TError value) => new Result<TError>.Error(value);
}

Error message:

CSC : warning CS8785: Generator 'UnionGenerator' failed to generate source. It will not contribute to the output and compilation errors may occur as a result. Exception was of type 'ArgumentException' with message 'The hintName '.Result.g.cs' of the added source file must be unique within a generator. (Parameter 'hintName')'.

The source generator uses the same file name for both Result<T, TError> and Result<TError>:

        context.AddSource(
            $"{unionRecord.Namespace}.{unionRecord.Name}.g.cs",
            SourceText.From(union, Encoding.UTF8)
        );

I would like to update it to:

        context.AddSource(
            unionRecord.TypeParameters.Count == 0
             ? $"{unionRecord.Namespace}.{unionRecord.Name}.g.cs"
             : $"{unionRecord.Namespace}.{unionRecord.Name}.{unionRecord.TypeParameters.Count}.g.cs",
            SourceText.From(union, Encoding.UTF8)
        );