Rover: Update documentation

[chfriedrich98]

Update the rover docs to reflect the changes in the following PRs:

• [x] https://github.com/PX4/PX4-Autopilot/pull/23653
• [x] https://github.com/PX4/PX4-Autopilot/pull/23669

This PR the following improvements to the rover docs:

• Restructure Drive Modes into Auto and Manual modes.
• Major update to the documentation of differential rovers. The differential module received some big updates with the support for new manual modes (Stabilized and Position). Due to these new modes the tuning process for differential rovers can be streamlined which is now documented in detail as a step by step guide going through the parameters/setup for each mode. Each mode successively adds more autopilot support (Manual > Acro > Stabilized > Position > Auto) and with it more parameters to set. The user guide now also includes tips/suggestions on how to tune the individual parameters, making it easier to set up the vehicle.
• Updated all graphics with a common color theme that works in both dark and light mode.

[chfriedrich98]

~~Note: This PR is ready for review, but merging it will have to wait until https://github.com/PX4/PX4-Autopilot/pull/23669 is merged. This will also fix the missing anchor for RD_MAX_SPEED.~~ PR was merged.

[hamishwillee]

@chfriedrich98 Thanks for this

1. I've added a lot of notes, mostly about tailoring for audience. I think you need to present this as high level as possible first, so that anyone can determine the main point with very little understanding of control theory.
2. Really love the diagrams
3. New structure makes a lot of sense, at least for now. I do wish the tuning could go in flight mode docs, but I think this will always be hard since the tuning depends on the vehicle. We might in future create a stand-alone tuning doc for each rover type.
4. In terms of subediting, most of this is docs-consistency:
   • I use sentence breaks for lines.
   • I refer to mode as Position mode with that casing.
   • The "note" type is not supported - we have to use info or tip for these.
   • I added back an image you deleted. Ignore it for now - this is because it breaks the translation builds if this does not exist, and I can't fix that yet due to a problem in our translation tool. They are working on it.

PS YOu might not agree with all this, or it might not all be practical. But let's see what you think - compromise is possible :-)

[github-actions[bot]]

No flaws found

[hamishwillee]

@chfriedrich98 Love the structure and new images. In particular the step by step instructions are much better - I think someone who doesn't know that much about rovers could do most of these.

There are some FYIs and couple of cases where we might add information inline. I'm going to merge because I like this a lot, and follow on changes are likely to be fairly small. Thank you.