Fix automations listening to HOMEASSISTANT_START (#6936)

* Fire EVENT_HOMEASSISTANT_START automations off right away while starting

* Actually have core state be set to 'starting' during boot

* Fix correct start implementation

* Test and deprecate event automation platform on start

* Fix doc strings

* Remove shutting down exception

* More strict when to mark an instance as finished

* Add automation platform to listen for start/shutdown

* When we stop we should wait till it's all done

* Fix testing

* Fix async bugs in tests

* Only set UVLOOP when hass starts from CLI

* This hangs normal asyncio event loop

* Clean up Z-Wave node entity test

homeassistant/bootstrap.py

@@ -74,8 +74,6 @@ def async_from_config_dict(config: Dict[str, Any],
     This method is a coroutine.
     """
     start = time()
-    hass.async_track_tasks()
-
     core_config = config.get(core.DOMAIN, {})
 
     try:
@@ -140,10 +138,10 @@ def async_from_config_dict(config: Dict[str, Any],
             continue
         hass.async_add_job(async_setup_component(hass, component, config))
 
-    yield from hass.async_stop_track_tasks()
+    yield from hass.async_block_till_done()
 
     stop = time()
-    _LOGGER.info('Home Assistant initialized in %ss', round(stop-start, 2))
+    _LOGGER.info('Home Assistant initialized in %.2fs', stop-start)
 
     async_register_signal_handling(hass)
     return hass