Refactor JDR: remove some of the usages of JavaDescriptorResolver class
Refactor JDR: add explicit binding between java classes and packages for their statics

Get rid of Kind in JavaPackageFragmentDescriptor and create subclass which exposes additional function
Add method in JavaClassDescriptor to get correponding package fragment
Remove JavaDescriptorResolver from context
Remove PackageFragmentDescriptor#getProvider method

PackageFragmentProvider should be hidden from the client of PackageFramentDescriptor
Add validation for binding between java classes and corresponding package fragments
AbstractInsertImportOnPasteTest: use test framework to create correct file structure for java files