Mqtt light refactor (#18227)

* Rename mqtt light files

* Refactor mqtt light

* Remove outdated testcase

* Add backwards compatibility for MQTT discovered MQTT lights.
Refactor according to review comments.

tests/components/light/test_mqtt.py

@@ -585,7 +585,8 @@ async def test_sending_mqtt_commands_and_optimistic(hass, mqtt_mock):
                                                'effect': 'random',
                                                'color_temp': 100,
                                                'white_value': 50})
-    with patch('homeassistant.components.light.mqtt.async_get_last_state',
+    with patch('homeassistant.components.light.mqtt.schema_basic'
+               '.async_get_last_state',
                return_value=mock_coro(fake_state)):
         with assert_setup_component(1, light.DOMAIN):
             assert await async_setup_component(hass, light.DOMAIN, config)
@@ -1063,3 +1064,20 @@ async def test_discovery_removal_light(hass, mqtt_mock, caplog):
 
     state = hass.states.get('light.beer')
     assert state is None
+
+
+async def test_discovery_deprecated(hass, mqtt_mock, caplog):
+    """Test removal of discovered mqtt_json lights."""
+    entry = MockConfigEntry(domain=mqtt.DOMAIN)
+    await async_start(hass, 'homeassistant', {'mqtt': {}}, entry)
+    data = (
+        '{ "name": "Beer",'
+        '  "platform": "mqtt",'
+        '  "command_topic": "test_topic"}'
+    )
+    async_fire_mqtt_message(hass, 'homeassistant/light/bla/config',
+                            data)
+    await hass.async_block_till_done()
+    state = hass.states.get('light.beer')
+    assert state is not None
+    assert state.name == 'Beer'