[pid_controller] Update tests (backport #1538)

[mergify]

Main changes

• Follow up of [pid_controller] Fix logic for feedforward_mode with single reference interface #1520, added new test for two joints, two interfaces.
• Updated some of existing tests with additional test validation steps.

---

This is an automatic backport of pull request #1538 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of b24b310 has failed:

On branch mergify/bp/humble/pr-1538
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit b24b310.
  (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:   pid_controller/CMakeLists.txt
	new file:   pid_controller/test/test_pid_controller_dual_interface.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   pid_controller/src/pid_controller.cpp
	both modified:   pid_controller/test/pid_controller_params.yaml
	both modified:   pid_controller/test/test_pid_controller.cpp
	both modified:   pid_controller/test/test_pid_controller.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

[codecov]

Codecov Report

Attention: Patch coverage is 72.34043% with 26 lines in your changes missing coverage. Please review.

Project coverage is 66.89%. Comparing base (92c47bd) to head (0c03827).
Report is 2 commits behind head on humble.

Files with missing lines	Patch %	Lines
...roller/test/test_pid_controller_dual_interface.cpp	72.91%	0 Missing and 13 partials ⚠️
pid_controller/test/test_pid_controller.cpp	66.66%	0 Missing and 11 partials ⚠️
pid_controller/src/pid_controller.cpp	50.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1545      +/-   ##
==========================================
+ Coverage   66.84%   66.89%   +0.05%     
==========================================
  Files         114      115       +1     
  Lines       13459    13533      +74     
  Branches     8334     8367      +33     
==========================================
+ Hits         8996     9053      +57     
+ Misses       1436     1428       -8     
- Partials     3027     3052      +25     

Flag	Coverage Δ
unittests	66.89% <72.34%> (+0.05%)	⬆️

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

Files with missing lines	Coverage Δ
pid_controller/test/test_pid_controller.hpp	81.03% <100.00%> (+1.59%)	⬆️
pid_controller/src/pid_controller.cpp	71.55% <50.00%> (+3.98%)	⬆️
pid_controller/test/test_pid_controller.cpp	47.07% <66.66%> (-1.48%)	⬇️
...roller/test/test_pid_controller_dual_interface.cpp	72.91% <72.91%> (ø)

... and 2 files with indirect coverage changes

[saikishor]

LGTM