purePursuit: migrate parameters to library

[chfriedrich98]

Solved Problem

The pure pursuit library introduced in #23387 requires some parameters that are currently defined in the ackermann module.
Migrating them to the library itself avoids having to redifine the same parameters for every module that uses the pure pursuit library in the future.
This effects the following parameters:

Parameter	Description	Unit
RA_LOOKAHD_GAIN $\rightarrow$ PP_LOOKAHD_GAIN	Main tuning parameter	-
RA_LOOKAHD_MAX $\rightarrow$ PP_LOOKAHD_MAX	Maximum value for the look ahead radius	m
RA_LOOKAHD_MIN $\rightarrow$ PP_LOOKAHD_MIN	Minimum value for the look ahead radius	m

[sfuhrer]

Looks like a clean iteration!

[hamishwillee]

@chfriedrich98 Good change.

FYI If you ever touch a parameter name, worth doing a search in the docs. If you add a parameter think "what difference might this make to end users" because perhaps new docs are needed.

The reason I note this is that the parameters auto updated and broke some links you fixed up previously in PX4/PX4-user_guide#3265.

I do plan to add some automation to remind developers, and perhaps move docs into this repo so you might find them with search and replace. Ultimately though we need to think about what end-user impacts changes might have.

P.S. Should also do search replace in the source - because these also mentioned in https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/pure_pursuit/PurePursuit.hpp#L98-L100

[chfriedrich98]

@hamishwillee Thanks for the reminder!
I intended to fix the parameter names with the rover restructure in PX4/PX4-user_guide#3311, but it makes sense to update it immediately to avoid any confusion in the meantime.

P.S. Should also do search replace in the source - because these also mentioned in https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/pure_pursuit/PurePursuit.hpp#L98-L100

The fix for that is part of this PR: https://github.com/PX4/PX4-Autopilot/pull/23470/files.