Tools: autotest: Test guided altitude commands in Plane

[Ryanf55]

Purpose

Add a test for master to preserve existing behavior of planes guided SET_POSITION_TARGET_GLOBAL_INT support where you set the bitmask to only change the vehicle altitude.

This is to be sure that the small cleanup in #28479 does not cause regressions.
As far as I can tell, the guided change altitude plane API in MAVLink is not tested in CI.

Details

The existing SetpointGlobalPos class is used on copter and rover tests, but not in Plane. Although it has some conditions for plane in the code, those are likely leftovers from something else. None of the existing tests will pass on plane because they aren't implemented.

I'm hung up right now on why

• The MAV_FRAMES_TO_TEST list includes MAV_FRAME_GLOBAL, but the to_alt_frame function does not include a converter.
• If the vehicle type is plane, FS_GCS_ENABLE cannot be set to 0
• Whether it's ok to call AutoTestPlane.fly_home_land_and_disarm in vehicle_test_suite.TestSuite, which couples the classes

Logs right now show that the vehicle is trying to climb to 750m, starting at CMAC, and I suspect it's because MAV_FRAME_GLOBAL is not having the home altitude taken off.

Logs

ArduPlane-SetpointGlobalPos.txt