support IOLoop.close() when called after asyncio.run

Start with the test_inproc_specific_different_threads failure in distributed/comm/tests/test_comms.py and the IOLoop.close() traceback. Inspect the cleanup of IOLoop._ioloop_for_asyncio when AbstractEventLoop.close() has already run; done means the reported close sequence completes without a KeyError.

I've been using the following function to run the distributed test suite:

def _run_and_close_tornado(async_fn, /, *args, **kwargs):
    tornado_loop = None

    async def inner_fn():
        nonlocal tornado_loop
        tornado_loop = IOLoop.current()
        return await async_fn(*args, **kwargs)

    try:
        return asyncio.run(inner_fn())
    finally:
        tornado_loop.close(all_fds=True)

Which has worked great with non-overlapping calls to IOLoop.current(), however I recently introduced an overlapping call, which results in a KeyError:

____________________ test_inproc_specific_different_threads ____________________

    @gen_test()
    async def test_inproc_specific_different_threads():
>       await check_inproc_specific(run_coro_in_thread)

distributed/comm/tests/test_comms.py:457: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
distributed/comm/tests/test_comms.py:431: in check_inproc_specific
    await asyncio.gather(*futures)
distributed/comm/tests/test_comms.py:447: in run_coro_in_thread
    return await asyncio.to_thread(run_and_close_tornado, run_with_timeout)
/usr/share/miniconda3/envs/dask-distributed/lib/python3.10/asyncio/threads.py:25: in to_thread
    return await loop.run_in_executor(None, func_call)
/usr/share/miniconda3/envs/dask-distributed/lib/python3.10/concurrent/futures/thread.py:58: in run
    result = self.fn(*self.args, **self.kwargs)
distributed/utils.py:506: in run_and_close_tornado
    tornado_loop.close(all_fds=True)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <tornado.platform.asyncio.AsyncIOMainLoop object at 0x7f7a6addb280>
all_fds = True

    def close(self, all_fds: bool = False) -> None:
        self.closing = True
        for fd in list(self.handlers):
            fileobj, handler_func = self.handlers[fd]
            self.remove_handler(fd)
            if all_fds:
                self.close_fd(fileobj)
        # Remove the mapping before closing the asyncio loop. If this
        # happened in the other order, we could race against another
        # initialize() call which would see the closed asyncio loop,
        # assume it was closed from the asyncio side, and do this
        # cleanup for us, leading to a KeyError.
>       del IOLoop._ioloop_for_asyncio[self.asyncio_loop]
E       KeyError: <_UnixSelectorEventLoop running=False closed=True debug=False>

https://github.com/dask/distributed/actions/runs/5475797836/jobs/9972404903#step:19:2420

@bdarnell could you catch the KeyError so that I can run AbstractEventLoop.close() then IOLoop.close()?