[diff_drive] Remove unused parameter and add simple validation #abi-breaking

[christophfroehlich]

• Remove unused parameter wheels_per_side
• Update description of names parameters (looking for joint names, not link names).
• add simple validation to names parameters, this needs some rework of the tests
• let the load_diff_drive test use the yaml from the test file (which had two bugs)

This breaks ABI because of the class variable change, is this a bad idea to backport?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d915497) 47.43% compared to head (364d3c5) 47.47%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #958      +/-   ##
==========================================
+ Coverage   47.43%   47.47%   +0.03%     
==========================================
  Files          41       41              
  Lines        3862     3859       -3     
  Branches     1816     1814       -2     
==========================================
  Hits         1832     1832              
+ Misses        769      767       -2     
+ Partials     1261     1260       -1     

Flag	Coverage Δ
unittests	47.47% <100.00%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...de/diff_drive_controller/diff_drive_controller.hpp	100.00% <ø> (ø)
...iff_drive_controller/src/diff_drive_controller.cpp	42.85% <100.00%> (+0.45%)	⬆️

[bmagyar]

Wonderful, thank you!

[bmagyar]

I think we should backport to Iron. Let's leave Humble as-is