[JTC] Convert lambda to class functions (backport #945)

[mergify]

This is an automatic backport of pull request #945 done by Mergify.
Cherry-pick of 833ed7f has failed:

On branch mergify/bp/iron/pr-945
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Changes to be committed:
	modified:   joint_trajectory_controller/include/joint_trajectory_controller/joint_trajectory_controller.hpp
	modified:   joint_trajectory_controller/src/joint_trajectory_controller.cpp
	modified:   joint_trajectory_controller/test/test_trajectory_controller.cpp
	modified:   joint_trajectory_controller/test/test_trajectory_controller_utils.hpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   joint_trajectory_controller/include/joint_trajectory_controller/tolerances.hpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 71.99%. Comparing base (9b5e04a) to head (0f29b46).

Additional details and impacted files

@@            Coverage Diff             @@
##             iron    #1015      +/-   ##
==========================================
- Coverage   72.72%   71.99%   -0.73%     
==========================================
  Files          40       40              
  Lines        3505     3503       -2     
  Branches     1750     1750              
==========================================
- Hits         2549     2522      -27     
- Misses        659      683      +24     
- Partials      297      298       +1     

Flag	Coverage Δ
unittests	71.99% <93.33%> (-0.73%)	⬇️

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

Files	Coverage Δ
...jectory_controller/joint_trajectory_controller.hpp	100.00% <100.00%> (ø)
...ory_controller/src/joint_trajectory_controller.cpp	79.91% <100.00%> (-0.15%)	⬇️
...include/joint_trajectory_controller/tolerances.hpp	75.67% <0.00%> (ø)

... and 2 files with indirect coverage changes