Investigation: Support upcoming MAVLink BATTERY_STATUS_V2 (369) message

## Feature request The goal of this issue is to align on how ArduPilot will support the ([currently in-development](https://mavlink.io/en/messages/development.html#BATTERY_STATUS_V2)) MAVLink message BATTERY_STATUS_V2 (369). (If recording this discussion as context isn't a sanctioned use of AP github issues, please just close this issue.) ### Platform - [x] All - [ ] AntennaTracker - [ ] Copter - [ ] Plane - [ ] Rover - [ ] Submarine ### Additional context (This work began as a DM between @hunt0r and @peterbarker . I've tried to recreate any important context from that here for future reference.) https://github.com/mavlink/rfcs/pull/19 is a related RFC regarding battery stuff in MAVLink.