Feature request: real time ground station barometric pressure updates.

#### Issue details
Update barometric ground pressure during long flights:
Suitable hardware:
The Yocto-Altimeter-V2 device is a USB altimeter : it will give you an altitude estimate based on atmospheric pressure. The Yocto-Altimeter-V2 is precise enough to detect 10cm altitude changes. It will also give you the current pressure and temperature .
It is using the ICP-10100 sensor.
Supported Operating Systems:Windows (PC + IoT), Linux (Intel + ARM), macOS, Android.
That way the ground station can update the barometric ground pressure during long flights.
It should also combat barometer drift.

#### Platform
[ ] All
[ ] AntennaTracker
[X] Copter
[X] Plane
[ ] Rover
[ ] Sub

No files, tests, or entry points are identified. First trace how the C# Mission Planner handles ground barometric pressure for Copter and Plane, then assess how the Yocto-Altimeter-V2 and ICP-10100 could provide live pressure on the listed platforms. Define the observable result needed to confirm drift correction.

Written by the indexing model from the issue text.