a real core shutdown of a CQ until such requests are done

GPR Buffers need to be destroyed, not directly freed, otherwise it leaks reference counted backing slices.

- use after free for resource quota
- stuck-in-combiner-lock bug for End2endTest.ClientCancelsBidi/1 under
  asan/epoll
- fixes clang-format stuff for a few files

Almost fixes #8753 (which still needs a test).

Otherwise, a null closure could be executed to reclaim, the reclaimation
finished edge would never be executed, and a future allocation will
stall forever.