Flash savings ideas : features/drivers to disable/remove to save flash

[rmackay9]

AP's flash size is constantly growing as new features and drivers are added but unfortunately the STM32 autopilot's CPUs flash size is not keeping up. This means we need to disable or remove lesser used features from many boards.

This issue is to collect ideas (primarily from members of the core dev team) on features/drivers they think could be sacrificed.

Note we have a few ways to reduce flash:

1. move the feature/driver to be disabled by default thus forcing users to rely on the custom build server
2. migrate the feature to Lua forcing the user to load a Lua script
3. completely remove the feature or driver

Suggestions include:

• Generator (suggested by PeterB)
• External AHRS (suggested by PeterB, Tridge)
• Avoid ADSB copter flight mode (suggested by Randy)
• AP_GPS_GSOF once we have it available as an EAHRS (from RyanF)

[Ryanf55]

• AP_GPS_GSOF once we have it available as an EAHRS.

+1 on EAHRS

[timtuxworth]

Plane: suggesting all of these could be custom build server options only.
ICE
Precision Landing
Gimbals (except for Mount and Servo Gimbal)
VTX
Generator

[amilcarlucas]

Winch
Exotic ESCs

[peterbarker]

I've used some of these ideas in https://github.com/ArduPilot/ardupilot/pull/28226/files - thanks!