[gripper] Add test for effort gripper controller

[chama1176]

Add test for effort gripper controller.

Fix #764

GripperController uses template parameters, so I used type-parameterized tests.
https://github.com/google/googletest/blob/main/docs/advanced.md#type-parameterized-tests
https://en.cppreference.com/w/cpp/types/integral_constant

[codecov-commenter]

Codecov Report

Merging #769 (3226ad2) into master (e7f9962) will decrease coverage by 4.90%.
Report is 365 commits behind head on master.
The diff coverage is 25.91%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #769      +/-   ##
==========================================
- Coverage   35.78%   30.88%   -4.90%     
==========================================
  Files         189        7     -182     
  Lines       17570      832   -16738     
  Branches    11592      505   -11087     
==========================================
- Hits         6287      257    -6030     
+ Misses        994      133     -861     
+ Partials    10289      442    -9847     

Flag	Coverage Δ
unittests	30.88% <25.91%> (-4.90%)	⬇️

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

Files Changed	Coverage Δ
...ontroller/test/test_load_diff_drive_controller.cpp	11.11% <0.00%> (ø)
...ive_controller/test/test_diff_drive_controller.cpp	12.66% <7.81%> (ø)
diff_drive_controller/src/odometry.cpp	42.16% <11.11%> (ø)
diff_drive_controller/src/speed_limiter.cpp	46.55% <11.11%> (ø)
...iff_drive_controller/src/diff_drive_controller.cpp	47.13% <46.94%> (ø)
...de/diff_drive_controller/diff_drive_controller.hpp	100.00% <100.00%> (ø)
...troller/include/diff_drive_controller/odometry.hpp	100.00% <100.00%> (ø)

... and 189 files with indirect coverage changes

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[bmagyar]

Thank you!

I used gmock for many years but never came across typed tests, you learn something new every day! This is very elegant and clean, thanks!