Tighter Home Assistant integration, with vehicle control

[deece]

This patch series provides tighter integration with Home Assistant, including:

• Automatic discovery of sensors via MQTT (provides long term statistics in Home Assistant, as well as squelching some warnings from HA)
• Persistent MQTT connections, rather than setting up and tearing down the connection for each status update
• Unique(er) MQTT client IDs, to avoid bumping off other clients connected to the same server
• Allows the use of the Home Assistant Tesla Fleet integration to start/stop/control charging, providing a simpler (but still more complex than I would like) path to set up the system