Rover: Use name 'destination' (not desired location)

[hunt0r]

Summary

Improve code clarity by aligning Rover on term 'destination' (not "desired location"). This corresponds to PR-set #32883 #32884 #32886 #32887 #32888 which do the same in AR_WPNav.

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

./Tools/scripts/size_compare_branches.py --vehicle=rover --board=CubeOrange

Board,rover
CubeOrange,*

I am trusting that Rover's autotests cover all modes, although I have not verified that myself. The fact that it compiles already demonstrates the rename was successful (at least for all compiled-in code paths).

Description

Fixes a few comments which contribute non-obvious information. Removes self-evident ones.