Support nameof() in CallerArgumentExpression

[CommonLoon102]

Without nameof(), it is not possible to rename parameter names safely. Currently, if I try to use nameof(), it says that "The name 'a' does not exist in the context."

https://weblogs.asp.net/dixin/csharp-10-new-feature-callerargumentexpression-argument-check-and-more

void Function(int a, TimeSpan b, [CallerArgumentExpression(nameof(a))] string c = "", [CallerArgumentExpression("b")] string d = "")
{
    Console.WriteLine($"Called with value {a} from expression '{c}'");
    Console.WriteLine($"Called with value {b} from expression '{d}'");
}

[alrz]

This is championed at dotnet/csharplang#373