NPFG: Add fallback for corner cases

[KonradRudin]

Solved Problem

The NPFG controller can't produce reliable roll setpoints when the wind estimation is not yet valid and the ground speed is close to zero or the vehcile is pushed back by the wind. This is a more general fix for #22003

Fixes #{Github issue ID}

Solution

• Add a new function evaluating if the npfg controller is able to produce reliable roll setpoint.
• Make a smooth transition from using the npfg output to keeping the current roll angle when the npfg output becomes unreliable.

Changelog Entry

For release notes:

Feature Add NPFG fallback for cornercases without valid wind estimates

[tstastny]

@KonradRudin thanks for the sanitizer! great to handle these cases now. However -- see the comment about blending to zero instead of last roll setpoint. I approved because I'll be out of office and unable to approve later... but I actually think blending to zero is the better solution in the degraded input cases. If there are strong reasons I am wrong about this .. please feel free to discuss also with @RomanBapst and @sfuhrer and you three can override my opinion ;)

[KonradRudin]

Rebased on main

[sfuhrer]

As discussed I would add some user notification when the factor drops below 1 (but has been above 1 before).
And I would consider reducing COM_VEL_FS_EVH by default a bit, as it would be bad if NPFG doesn't control roll any more because the estimator reports a very high velocity uncertainty but there is no failsafe action triggered.

[sfuhrer]

Looks good now! Let's clean up the commits and bring it in then.

[KonradRudin]

Squashed the commits and rebased on main.

[sfuhrer]

@KonradRudin can you check if the CI failures are real?