BattMonitor: DroneCAN batteries report and log state-of-health percentage

[rmackay9]

This adds state-of-health percentage logging for DroneCAN battery backends. I've reduced the scope of this PR by removing the reporting via MAVLink.

The DroneCAN DSDL message already includes this field and the Tattu DroneCAN batteries send the value but we haven't made use of it until now.

This has been tested on real hardware (CubeOrangePlus with a Tattu battery). Below is a screenshot showing the SOH of 95%.

[IamPete1]

I think this looks basically OK, but we will have to merge the MAVLink change first so we can do the sub-module shuffle.

[hendjoshsr71]

Note for DroneCAN we do have new messages that will be implemented eventually..... (---> looks at self <----)

Here those are : https://github.com/dronecan/DSDL/pull/7/files
For some reason they A.) got merged into the "ardupilot dsdl" & B.) dont show on the dronecan wiki page.

MAVLink
There are newer battery status messages to mirror those CAN messages.
Here is the newer Battery_Status message : https://mavlink.io/en/messages/development.html#BATTERY_STATUS_V2

It doesn't include state of health since that changes quite slowly.

Generally, adding fields to Battery_Status has been a nonstarter since it is already too large of a message.... (Nothing has been added in 4 years to it.)

I did check that the SMART_BATTERY_INFO Doesn't Include : https://mavlink.io/en/messages/common.html#SMART_BATTERY_INFO

[davidbuzz]

I think this should go in