function expressions search: accept functional functional interfaces inheritors (IDEA-128086)
find functional interface on arrow/dbl column (IDEA-122033)
testdata for IDEA-127124
remove unused testdata
IDEA-132967 (TypeMayBeWeakened incorrectly advises weakening to java.util.function.Function on method which is used by reference)
clean groovy stub dirs via renameAndDelete less frequently
don't hold AST references in SymbolCollectingProcessor cache
revert "possibility to have several stub trees in a file"