Add waypoint duration to the trajectory deep copy unit test

[AndyZe]

Previously, only joint positions were tested.

This should settle the discussion here (PR #2957). The duration deep copy was correct, it seems.

[codecov]

Codecov Report

Merging #2961 (2d812e5) into master (4db626d) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2961      +/-   ##
==========================================
- Coverage   61.59%   61.54%   -0.04%     
==========================================
  Files         370      370              
  Lines       33101    33104       +3     
==========================================
- Hits        20386    20372      -14     
- Misses      12715    12732      +17     

Impacted Files	Coverage Δ
.../ompl_interface/src/detail/constrained_sampler.cpp	43.91% <0.00%> (-17.07%)	⬇️
...dl_kinematics_plugin/src/kdl_kinematics_plugin.cpp	75.66% <0.00%> (-2.24%)	⬇️
...raint_samplers/src/default_constraint_samplers.cpp	79.60% <0.00%> (-0.28%)	⬇️
...t_setup_assistant/src/tools/moveit_config_data.cpp	15.40% <0.00%> (-0.05%)	⬇️

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