[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/humble/pr-945
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit 833ed7f.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   joint_trajectory_controller/include/joint_trajectory_controller/joint_trajectory_controller.hpp
	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
	both modified:   joint_trajectory_controller/src/joint_trajectory_controller.cpp

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

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[codecov]

Codecov Report

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

Project coverage is 72.53%. Comparing base (6276f96) to head (6e282de).

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1014      +/-   ##
==========================================
+ Coverage   72.12%   72.53%   +0.40%     
==========================================
  Files          40       40              
  Lines        3555     3553       -2     
  Branches     1786     1786              
==========================================
+ Hits         2564     2577      +13     
+ Misses        685      670      -15     
  Partials      306      306              

Flag	Coverage Δ
unittests	72.53% <93.33%> (+0.40%)	⬆️

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	80.05% <100.00%> (-0.27%)	⬇️
...include/joint_trajectory_controller/tolerances.hpp	75.67% <0.00%> (ø)

... and 2 files with indirect coverage changes