Close #10042: functools.total_ordering now handles NotImplemented

(Patch by Katie Miller)
Issue #18594:  Fix the fallback path in collections.Counter().
merge
Issue #19137: The pprint module now correctly formats instances of set and
frozenset subclasses.
Issue #19137: The pprint module now correctly formats instances of set and
frozenset subclasses.
Issue #19132: The pprint module now supports compact mode.
Closes #19139: Changed usage of __VENV_NAME__ and added __VENV_PROMPT__.
Close #19078: memoryview now supports reversed

Patch by Claudiu Popa