ECS0600 is too coarse

[rjmurillo]

ECS0600 is intended to do two things:

1. Promote the nameof operator when the symbol name is the same as the value (e.g. var Name = nameof(Name))
2. Stop inlining the constant value during IL creation

This feels like two separate rules. The first is the existing ECS0600 but is a bit pedantic and should be moved to Suggestion. A new analyzer for the second case (e.g., ECS0601) that is a warning and only for publicly visible or Internalsvisibleto symbols

CC @MattKotsenas