More fixes to Python bindings docstrings

[sea-bass]

#2471 was not enough... fixing more stuff, and also added missing docstrings.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (faa4795) 50.35% compared to head (b8f679d) 50.82%.
Report is 4 commits behind head on main.

❗ Current head b8f679d differs from pull request most recent head edabf3c. Consider uploading reports for the commit edabf3c to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2474      +/-   ##
==========================================
+ Coverage   50.35%   50.82%   +0.47%     
==========================================
  Files         390      391       +1     
  Lines       31954    32125     +171     
==========================================
+ Hits        16087    16324     +237     
+ Misses      15867    15801      -66     

Files	Coverage Δ
.../moveit_core/robot_trajectory/robot_trajectory.cpp	77.15% <ø> (ø)

... and 8 files with indirect coverage changes

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