Diagnostics dont work because they dont have access to the event loop

[jopotochnykorbit]

To reproduce

1. Fork/Clone this project
2. Run the server using a websocket, e.g. poetry run jedi-language-server --ws --verbose --log-file .logs.txt
3. Using any client (or use the monaco-languageclient example, instructions to which can be found here, get the client to emit one of textDocument/didOpen, textDocument/didChange, textDocument/didSave, textDocument/didClose or textDocument/hover.
4. The server should spit out many errors that are all RuntimeError: There is no current event loop in thread X

When I forked this project and ran it locally, using the monaco-languageclient react client example as a client, I kept getting crashes when the diagnostic actions (e.g. textDocument/didOpen, textDocument/didChange, textDocument/didSave, textDocument/didClose and textDocument/hover) were being emitted. The error I was getting was:
RuntimeError: There is no current event loop in thread X

After a few hours of debugging, I realized that it was coming from this file, where the Diagnostic methods are being run in a thread using Timer. This leads to that thread not having an event loop to send things via websocket.

I fixed this by replacing lines 68 - 80 with:

async def run() -> None:
    with lock:
        del timers[key]
    return func(*args, **kwargs)

with lock:
    old_timer = timers.get(key)
    if old_timer:
        old_timer.cancel()

    timer = threading.Timer(interval_s, asyncio.run_coroutine_threadsafe, args=(run(), asyncio.get_running_loop()))
    timers[key] = timer
    timer.start()

This ensures that the thread has an event loop to use, and changing it to this made the diagnostic actions work again.