Add Water Heater platform to MQTT integration (#93644)

* Add Water Heater entity to MQTT

* Adding tests for Water Heater

* Remove duplicate line and unneeded var declaration

* Remove target temp range and away mode

* Move common Temperature Control conf to const

* Remove unnecessary platform schema and temp check

* Add common value template key test

* Use MqttTemperatureControl in Water Heater

* Move operation mode out of MqttTemperatureControl

* Remove unecessary attribute declaration

* Remove default min/max temp and auto init attr

* Fix mqtt water heater initial temp conversion

* Make async_set_temperature common

* Fix init temp comment

* Merge value_template_keys into get_with_templates

* Remove unnecessary operation_mode overriding

* Add async_set_temperature to water heater

* Fix docstring comments

tests/components/mqtt/test_climate.py

@@ -1333,6 +1333,9 @@ async def test_get_target_temperature_low_high_with_templates(
                     # By default, just unquote the JSON-strings
                     "value_template": "{{ value_json }}",
                     "action_template": "{{ value_json }}",
+                    "current_humidity_template": "{{ value_json }}",
+                    "current_temperature_template": "{{ value_json }}",
+                    "temperature_state_template": "{{ value_json }}",
                     # Rendering to a bool for aux heat
                     "aux_state_template": "{{ value == 'switchmeon' }}",
                     # Rendering preset_mode