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.

1. In the State change test, 123->0 will hit a c-core GPR_ASSERT if
debugging is enabled because 123 doesn't map to a state that can
be printed.
2. In the Server test, 8888 is sometimes unavailable, so we just use
a wildcard port.

The server cleanup method is untested.

The join() function that exposes it is only called by the internals of threading.py, and we don't hold a reference to the server thread to explicitly join() it, and I'm not sure we should add a reference just for this purpose.

Moreover, the threading.py only calls join(None), the code path in question isn't even exercised by the internals of threading.py. Its just there to make sure we properly follow the join(timeout) semantics.