- make closures know where they should be executed (eg, on a workqueue,
  or a combiner, or on an exec_ctx)
- this allows removal of a large number of trampoline functions that
  were appearing whenever we used combiners, and should allow for a much
  easier interface to combiner locks

- 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

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