Populate velocities and accelerations for multidof joint trajectories (backport #3635)

[mergify]

Description

If I were to use SetRobotTrajectoryMsg, to set a trajectory message, it appears that only positions are handled for multidof joints, and velocity/acceleration information is discarded.

This change handles the contents of multidof joint trajectories similarly to done here and populates the velocities and accelerations in the robot states. I've also taken the liberty of adding a test to ensure that the multidof joint trajectory positions and accelerations appear as expected.

This currently doesn't support angular/x or angular/y, for which I've added a comment noting this.

As a note, I tested this on Jazzy. I currently don't have a rolling build going, but I don't think things look that different in this part of the code base anyway.

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This is an automatic backport of pull request #3635 done by Mergify.

[codecov]

Codecov Report

❌ Patch coverage is 91.48936% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.23%. Comparing base (1ade0e9) to head (85c30ca).
⚠️ Report is 2 commits behind head on jazzy.

Files with missing lines	Patch %	Lines
...eit_core/robot_trajectory/src/robot_trajectory.cpp	87.50%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            jazzy    #3638      +/-   ##
==========================================
+ Coverage   46.18%   46.23%   +0.05%     
==========================================
  Files         718      718              
  Lines       59109    59156      +47     
  Branches     7589     7595       +6     
==========================================
+ Hits        27292    27343      +51     
+ Misses      31652    31648       -4     
  Partials      165      165              

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