Navigator: Use hysteresis for neutral gimbal command delay + some refactoring

[MaEtUgR]

Solved Problem

I came across #25551 too late, but realized it's the implementation of a hysteresis/delay and there might be an opportunity to simplify the navigator for better readability, so I’m suggesting this follow-up.

Solution

• Use the existing hysteresis library for the neutral gimbal command delay, it uses a bit more RAM but is well tested and has a simple interface.
• Unroll tiny functions that are only called once and for which the reader needs to jump to the end of the file and back.
• Reduce hrt_absolute_time() calls which all have an insignificantly different timestamp as a result and reuse a loop timestamp instead.

Changelog Entry

Navigator: Use hysteresis for neutral gimbal command delay + some refactoring

Test coverage

Not tested, it should be a pure refactor. The thing that would be nicest to verify is that I used the hysteresis correctly.

[perrrre]

Would be nice to put a comment that the time from true is 0, or maybe add this?

_gimbal_neutral_hysteresis.set_hysteresis_time_from(true, 0);