close() could race with epoll_ctl(); pretend to be polling while adding
to the epoll set to prevent this

Prevents TSAN races in iomgr shutdown code

Prevents a race whereby we start deleting the freelist before it's used

Do this by ensuring that the alarm callback has had a chance to run on a
call before returning status to the application.

If we do not do this:
- the server alarm could be scheduled and run
- it will write a RST_STREAM with a status that loses the deadline
  exceededness (because that is unexpressable in HTTP2 error codes)
- it will be received by the client and processed
- the client will return an INTERNAL error (the lossy re-encoding of the
  server status), and then run its alarm handler to set the status to
  something else

Handle the case where we recreate an auth context.

Add (opt-in) debugging for refcounts on auth contexts.

This brings the Windows port more in-par with Linux. We're now making sure all of the pollsets are going to return immediately before calling the shutdown callback.

- Allow ablity to specify the length for decoding.
- Allow for non-padded encodings to be decoded properly.

Clean up anything that failed