Refactor shared mqtt schema's to new module (#117944)

* Refactor mqtt schema's to new module

* Remove unrelated change

homeassistant/components/mqtt/humidifier.py

@@ -53,7 +53,6 @@ from .const import (
 )
 from .debug_info import log_messages
 from .mixins import (
-    MQTT_ENTITY_COMMON_SCHEMA,
     MqttEntity,
     async_setup_entity_entry_helper,
     write_state_on_attr_change,
@@ -65,6 +64,7 @@ from .models import (
     ReceiveMessage,
     ReceivePayloadType,
 )
+from .schemas import MQTT_ENTITY_COMMON_SCHEMA
 from .util import valid_publish_topic, valid_subscribe_topic
 
 CONF_AVAILABLE_MODES_LIST = "modes"