++ introduce virtual file finder
++ KotlinClassFileIndex
Stubs for JetClassBody

This fixes some cases in getParent() behaved differently on stubs and ast
++ stubs for class body
++ KotlinClassFileHeader
REWORD: Add KotlinClassFileHeader#exists and better utilities
++ KotlinClassFileIndex. or utilities
REWORD: Restructure JetDecompiledData
Use new JetDecompiledData to navigate to declarations in decompiled files
Fix logic in JetQuickDocumentationProvider
++ KotlinFileViewProviderFactory or DecompiledUtils
Stub builder for classes

Also building stubs for properties
Extract CompiledStubBuilderBase
FIX