Problem

When battery scale significantly above 1 (battery far from full):

• first principle airspeed check giving false positives
• synthetic airspeed too high

This is caused by mixing different throttle units (some with, some without battery scaling) in both of these places.

Solution

change everything to use high-level TECS throttle setpoints which do not include battery scaling. this is more approprate here, as these setpoints reflect closely what we want the vehicle to do, whereas the battery scaling (which enters in FixedwingRateControl) is more of an implementation detail in comparison.

TODO:

• find a suitable alternative that also works in transitions -- TECS only runs in fixed wing, and we depend on airspeed being fused in transition already, so that in fixed wing it will not failsafe because OF is the only horizontal aiding and the loiter waypoint is above OF max height
  • very simple but maybe kind of ugly: give filtered tecs throttle to airspeed check, keep previous version in Add synthetic airspeed based on thrust #24522
• validate with all VTOL types that no edge case is broken
• validate in real life that it fixes the false positive airspeed failures
• clean up commits & description