Minor, delete outdated assertions in ImplementationBodyCodegen
Minor, remove code duplication in ImplementationBodyCodegen
Minor, remove unreachable code in CodegenContext#intoConstructor
Minor, store closure class name for debugging purposes

Strip package from the name up to the last slash, because slashes are not
allowed in a Name
Minor, add nullability annotations, toString(), remove unused methods
Refactor and rename ExpressionCodegen#generateFromResolvedCall
Minor, add NotNull to JetCoreEnvironment#getConfiguration

 #KT-5460 Fixed
Minor, swap parameters of AnalyzerWithCompilerReport#analyzeAndReport

 #KT-5459 Fixed