Implement push notifications for gateway

[starkillerOG]

Implement push server for the gateways.
Split out from PR #1288
Follow up of PR #1446

Test script:

import logging
import asyncio
from miio import Gateway, PushServer

_LOGGER = logging.getLogger(__name__)
logging.basicConfig(level="INFO")

gateway_ip = "192.168.1.IP"
token = "TokenTokenToken"


async def asyncio_demo(loop):
    def gateway_callback(action, params):
        _LOGGER.info("Gateway '%s' callback, params: '%s'", action, params)

    def subdevice_callback(action, params):
        _LOGGER.info("Subdevice '%s' callback, params: '%s'", action, params)
    
    push_server = PushServer(gateway_ip)
    gateway = Gateway(gateway_ip, token, push_server=push_server)
    
    await push_server.start()

    await loop.run_in_executor(None, gateway.alarm.subscribe_events)
    gateway.register_callback("DEMO_CB", gateway_callback)

    await loop.run_in_executor(None, gateway.discover_devices)
    
    for device in gateway.devices.values():
        device.register_callback("DEMO_CB", subdevice_callback)
        await loop.run_in_executor(None, device.subscribe_events)
    
    _LOGGER.info("Listening")
    
    await asyncio.sleep(60)

    push_server.stop()
    gateway.close()

if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(asyncio_demo(loop))

[starkillerOG]

@rytilahti this is the follow-up PR for the push server implementation for the gateway.
Could you review this and merge before the release this week?

[codecov-commenter]

Codecov Report

Merging #1459 (1450c1e) into master (4dd3cd8) will decrease coverage by 0.87%.
The diff coverage is 36.95%.

@@            Coverage Diff             @@
##           master    #1459      +/-   ##
==========================================
- Coverage   83.35%   82.48%   -0.88%     
==========================================
  Files         139      140       +1     
  Lines       13670    13897     +227     
  Branches     3248     3304      +56     
==========================================
+ Hits        11395    11463      +68     
- Misses       2057     2214     +157     
- Partials      218      220       +2     

Impacted Files	Coverage Δ
miio/gateway/devices/subdevice.py	33.14% <23.07%> (-3.74%)	⬇️
miio/gateway/alarm.py	47.72% <35.29%> (-7.83%)	⬇️
miio/gateway/gateway.py	44.44% <39.28%> (-3.15%)	⬇️
miio/gateway/gatewaydevice.py	69.23% <100.00%> (+2.56%)	⬆️
miio/push_server/__init__.py	100.00% <100.00%> (ø)
miio/push_server/server.py	24.62% <100.00%> (+1.14%)	⬆️
...io/integrations/vacuum/dreame/dreamevacuum_miot.py	74.38% <0.00%> (-4.36%)	⬇️
miio/__init__.py	100.00% <0.00%> (ø)
miio/cloud.py	33.33% <0.00%> (ø)

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[starkillerOG]

again a unrelated test failure about the utils module

[starkillerOG]

@rytilahti could you add this to the 5.12 milestone?

[rytilahti]

again a unrelated test failure about the utils module

Yeah, 3.11-dev checks on mac and windows are flaky, maybe I should disable them altogether :-(

[starkillerOG]

@rytilahti thank you very much for the review and the feedback!
I have processed everything.
Could you review again/merge?

(I am away this weekend so won't be able to work on this after tonight, if you have further suggestions, feel free to just make commits and merge the commits in this PR)

[rytilahti]

I updated the docs a bit but I suppose this is otherwise fine for now, let's get it merged! Thanks @starkillerOG!

[starkillerOG]

@rytilahti thank you very much for your help and suggestions, very glad we manged to get this merged before the new release :)