KT-6122 Code completion in when in enum extension methods suggests non-qualified enum entry names

 #KT-6122 Fixed
Fixed exception
KT-6407 Completing function with "tab" (replace) shouldn't insert parentheses when type arguments are present

 #KT-6407 Fixed
Corrections after review + one more test added
Fixed EA-63622 - IAE: FqName.validateFqName