Warn about unwrapFakeOverride in a comment
Simplify codegen for trait methods with implementations

- use existing framework (FunctionCodegen.generateMethod) which will take care
  of all subtleties of method generation (bridges, annotations, thrown
  exceptions, etc)
- call to "generateThisOrOuter" was not needed, since when we're generating
  delegation to TImpl, "this" is always "ALOAD 0"
Minor, move and rename getExceptions

Should only be used in FunctionCodegen from now on, because every method
generation should go through FunctionCodegen
Refactor bridges algorithm in codegen

- fix a typo (which apparently didn't matter)
- queue now always contains originals, no need to invoke getOriginal()
- no need to add current descriptor's original anymore, this was a hack working
  around a problem with trait-impl which was fixed by another change
- a small optimization: don't do anything for constructors
Generate bridges for fake overrides when needed

 #KT-3985 Fixed
 #KT-4145 Fixed
Consider all real functions, not only declarations in bridge codegen

There should be bridges to all of the functions present in bytecode
Minor, add bytecode text test on bridges for fake overrides
Minor, catch all exceptions in asm verification in tests

E.g. ClassFormatError
Refactor ImplementationBodyCodegen.getTraitImplementations()

Make it static, extract a method which finds an implementation in a trait for a
fake override
Rewrite bridge generation to Kotlin, make it abstract
Don't generate bridges in light classes mode
Generate bridges for trait implementations properly

The intent was to keep the bridge codegen model as simple as possible: we
should be able to figure out all necessary bridges only by a minimal interface
that FunctionHandle provides (isAbstract, isDeclaration, getOverridden)

Add different tests for bridges

 #KT-318 Obsolete
Minor, fix KotlinSignature of DFS methods