Test corrections noticed during pytest upgrade (#82579)

* Withing trigger a call to coordinator after init

* Stop discovery task on STOP event

* Stop dsmr connection task on STOP

* Use autospec in modem_serial tests

close on AioSerial is non async, and should not be mocked as a coroutine

* Make sure responder is specced correctly

tests/components/emulated_hue/test_init.py::test_setup_works
  /Users/joakim/src/hass/home-assistant/homeassistant/components/emulated_hue/__init__.py:119: RuntimeWarning: coroutine 'AsyncMockMixin._execute_mock_call' was never awaited
    protocol.close()

* Don't assume Pymodbus is the only thing logging

* Use gather instead of wait

```
homeassistant/components/homeassistant/__init__.py:208: DeprecationWarning: The explicit passing of coroutine objects to asyncio.wait() is deprecated since Python 3.8, and scheduled for removal in Python 3.11.
```

* Increase wait time for automation tests

Assuming exit within 1 seconds is unreasonable on a potentially loaded
test machine.

* Avoid changing app state after startup

tests/components/modbus/test_init.py

@@ -529,7 +529,7 @@ async def test_pb_service_write(
         data[do_write[DATA]],
     )
     if do_return[DATA]:
-        assert caplog.messages[-1].startswith("Pymodbus:")
+        assert any(message.startswith("Pymodbus:") for message in caplog.messages)
 
 
 @pytest.fixture(name="mock_modbus_read_pymodbus")