Move DebugProtoBuf to module "compiler-tests"

To help debug serialization-related code in compiler tests
Minor fix in tests for sources appearing in libraries
Minor, add toString() to OutputFile for debugging
Write KotlinSyntheticClass to generated classes for functions

That is SAM wrappers, callable reference wrappers, local functions and
anonymous functions
Write KotlinSyntheticClass to anonymous and local classes
Add tests that there's no PSI for all kinds of synthetic classes
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