AP_Mount: support gimbal_manager_status and do_gimbal_manager_configure

[rmackay9]

This supersedes PR #23713

This adds superficial support for two new mavlink messages meant to help de-conflict multiple mavlink devices attempting to control a gimbal. This is important so that development of QGC's camera/gimbal control screen can progress.

• GIMBAL_MANAGER_STATUS reports to the GCS which device is currently in control of the gimbal (e.g. sysid, compid)
• MAV_CMD_DO_GIMBAL_MANAGER_CONFIGURE allows a GCS to take or give-up control of the gimbal

The support is "superficial" because it does not actually reject gimbal control commands that comes from devices that are not in control. To comprehensively block commands we need to consolidate handling of more commands (including DO_SET_ROI) within the AP_Mount library instead of within GCS_MAVLink.

This has been lightly tested in SITL including:

• GIMBAL_MANAGER_STATUS message is returned in response to "long MAV_CMD_REQUEST_MESSAGE 281"
• MAV_CMD_DO_GIMBAL_MANAGER_CONFIGURE commands are consumed and correctly affect the sysid/compid returned in the above message especially when the special values are passed in for sysid (e.g. 0:no one in control, -1:leave unchanged, -2:set itself in control, -3:remove control if currently in control)

There's also a drive-by bug fix to the GIMBAL_MANAGER_INFORMATION gimbal_device_id instance field.

[MichelleRos]

All good for the blimp changes - sorry, I really need to do a lot of removal of unused code there...

[Davidsastresas]

Looking great, thank you!

[trolledbypro]

Hello all,
I am working on increasing MAVSDK compatibility with ArduPilot. My issue on their repo is mavlink/MAVSDK#2110. Through testing, I have discovered that MAVSDK sends DO_GIMBAL_MANAGER_CONFIGURE as part of the mission sequence:

Was this PR intended to allow DO_GIMBAL_MANAGER_CONFIGURE to work as a mission item, sent inside a mission sequence?. I do not see DO_GIMBAL_MANAGER_CONFIGURE as a supported command in https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Mission/AP_Mission.cpp.