[control-allocation] parameterize yaw margin

[somebody-once-told-me]

Solved Problem

There is a hard-coded magic-number yaw margin parameter in ControlAllocationDesaturation. Users might not be aware that the flight controller will give up a maximum of 15% of collective thrust for yaw when saturated.

Solution

This parameterizes and documents the yaw margin value.

Alternatives

We could also simply centralize and document the yaw margin as a static constexpr class member, instead of a user-facing parameter. This would require new builds when modifying the yaw margin value.

Two potential problems with the current change:

1. Addition of a public member getter variable only for unit testing (possible bad style).
2. Possible problems from usage of parameter in control loop?

Test coverage

Updated the ControlAllocationDesaturationTest to utilize the new parameter.

[bresch]

Looks good to me.
However, should we maybe set that one as a percentage?
if yes, you can add the tag * @unit % just above * @min 0.0, set the default to 15, max to 100 (or maybe a lower safe value? e.g.: 30%) and so on.

BTW, could you remove the diff in platforms/nuttx/NuttX/nuttx ?

[somebody-once-told-me]

@MaEtUgR is there anything else i can do to help with this PR?

[MaEtUgR]

The pr looks correct yes.
@somebody-once-told-me It'd be really valuable to know for what use/problem case you want to have this configurable compared to having a different value the "default". I assume most people will neither understand nor touch this parameter and hence it might be good to solve the problem you have either in a different way or by documenting what use case this configuration helps with.

Related to this I'm working on something I call limited airmode to essentially replace minimum thrust with a configurable authority for airmode: #22706 Maybe your issue can be solved with this as well.

[somebody-once-told-me]

@MaEtUgR Thanks for the review! I do not quite understand your PR yet, but I would definitely defer to that if this PR is merely a subset of yours, functionally. This PR is very specific and my use case is to simply set it to 0 (do not sacrifice altitude (e.g. drop) for yaw authority). If you feel strongly this is not going to provide any value apart from your change, I can close this and wait for yours. Do you happen to have an approximate ETA?