[analyzer] rename doesn't handle String interpolation

[asashour]

Rename the variable a to a$

String f() {
  var a = '';
  return '$a';
}

The actual result is '$a$', which should be '${a$}'. This happens with both IDEs.

Visual Studio Code calls the server textDocument/rename.

IntelliJ does it by itself. I believe it should also call the server to rename.

Handling special characters was hinted in the discussion around #22038