Move 20300.CBAT to `dronecan` section

[David-OConnor]

Hi! The cuav/equipment/power/20300.CBAT.uavcan power supply data seems more practical than the ones in uavcan/equipment/power. I'm designing a CAN-based power supply, and it's the best match to the data I'd like to output.

Thoughts on moving this to dronecan/equipment/power or similar? It was presumably designed with a specific device in mind, but it seems like a better general option than the ones in uavcan.

[tridge]

we could move it if we use OVERRIDE_SIGNATURE to prevent a signature change