What does this implement/fix?

Publishing "None" instead of "NaN" values for sensors in MQTT. This is to align with HASS's MQTT changes as it no longer seem to like them NaN values in sensor states and it's spamming the logs each time nan is published e.g.

ValueError: Sensor sensor.ld2410_sensor_g8_move_energy has device class 'None', state class 'None' unit '%' and suggested precision 'None' thus indicating it has a numeric value; however, it has the non-finite value: 'nan'
2024-11-08 15:43:41.169 ERROR (MainThread) [homeassistant] Error doing job: Task exception was never retrieved (None)
Traceback (most recent call last):
File "/usr/src/homeassistant/homeassistant/components/mqtt/entity.py", line 856, in _async_process_discovery_update
await discovery_update(payload)
File "/usr/src/homeassistant/homeassistant/components/mqtt/entity.py", line 1137, in discovery_update
self.async_write_ha_state()
File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 1005, in async_write_ha_state
self._async_write_ha_state()
File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 1130, in _async_write_ha_state
self.__async_calculate_state()
File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 1067, in __async_calculate_state
state = self._stringify_state(available)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 1011, in _stringify_state
if (state := self.state) is None:
^^^^^^^^^^
File "/usr/src/homeassistant/homeassistant/components/sensor/init.py", line 675, in state
raise ValueError(
ValueError: Sensor sensor.ld2410_sensor_g8_still_energy has device class 'None', state class 'None' unit '%' and suggested precision 'None' thus indicating it has a numeric value; however, it has the non-finite value: 'nan'

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code quality improvements to existing code or addition of tests
• Other

Related issue or feature (if applicable):

N/A

Pull request in esphome-docs with documentation (if applicable):

• Updated docs for esphome#7768 esphome-docs#4452

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040
• BK72xx
• RTL87xx

Example entry for config.yaml:

mqtt:
  broker: $mqtt_broker
  username: $mqtt_user
  password: $mqtt_password
  publish_nan_as_none: true

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.