In particular, this commit includes:
* Attempt to abstract access to FirSourceElement via FirModifier
* Add more visit functions to DeclarationCheckersDiagnosticComponent
* Add messages+factories for 4 modifier-related errors and warnings
* Introduce FirModifierChecker
Disable annotation rendering in default type and descriptor renderers.
Preserve annotations in Android and Serialization plugins.
Update error texts in ide tests.
Nullability annotations in Java descriptors are rendered with context-dependent renderer.
#KT-20258 Fixed
FenstonSingel