- there seems to be a code path that cleans up easy handles without
triggering DONE or DETACH events to the connection filters. This
would explain wh nghttp2 still holds stream user data
- add GOOD check to easy handle used in on_close_callback to
prevent crashes, ASSERTs in debug builds.
- NULL the stream user data early before submitting RST
- add checks in on_stream_close() to identify UNGOOD easy handles
Reported-by: Hans-Christian Egtvedt
Fixes#10936Closes#12562