Remove mimic tags and rename sim_ignition to sim_gazebo

[sea-bass]

I was trying to use this package on Rolling / Ubuntu 24.04 and ran into this problem.

Found it was related to ros-controls/ros2_control#1553, in which the <mimic> tags have been deprecated as this information is now looked up directly from URDF.

So these tags, and command interfaces, for mimic joints, should be removed.

---

BTW: This fixes Rolling CI because of a unit test that broke due to the above changes

... though the Coverage build seems to be failing for another reason. Seems to be ros-tooling/action-ros-ci#844

EDIT: fixed in #56

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I also took the liberty of renaming sim_ignition to sim_gazebo in accordance to my related PR to the Kortex repo: Kinovarobotics/ros2_kortex#228. But I can concede and pull that out to a future PR.

[sea-bass]

It does seem like ros2_control has thrown yet another curveball at us here... I'll take a look later if I can will myself to

[sjahr]

Damn, thanks!

[sea-bass]

This is the PR that broke things -- fixing now
ros-controls/ros2_control#1585

Of course, this means that non-rolling CI will now fail, so CI stuff will need to be modified to be on different branches, etc.

I recommend that someone with admin power branch out humble, iron, and jazzy branches and keep those respective distros' CI on those. Then, the top-level README with all the status badges should be updated.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.26%. Comparing base (743d20f) to head (2a735e6).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##            main      #54       +/-   ##
==========================================
+ Coverage   0.00%   40.26%   +40.26%     
==========================================
  Files          5       20       +15     
  Lines        352      524      +172     
  Branches       0       33       +33     
==========================================
+ Hits           0      211      +211     
+ Misses       352      308       -44     
- Partials       0        5        +5     

Flag	Coverage Δ
unittests	40.26% <100.00%> (+40.26%)	⬆️

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[sjahr]

Thank you @sea-bass !