Unused header cleanup

[henrygerardmoore]

This PR just removes unused headers, replacing them with different ones where necessary. It also standardizes using #include <gmock/gmock.h> as opposed to #include "gmock/gmock.h" (both were being used). Each commit is one package for convenience. The code still builds and the same tests seem to be failing as before. I don't notice any improvement in build speed, so this is just a style change.

I used the clangd extension in vscode for this, though had to ignore a select few of its suggestions which caused build failures (particularly with *_impl.hpp files and similar.

[henrygerardmoore]

Sorry about the force pushes, was rebasing to use the correct signing key.

[bmagyar]

Looking great! Thank you

[christophfroehlich]

LGTM 🙏

[saikishor]

LGTM

[bmagyar]

Now that the CI is finally healthier, let's see how it does here!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.57%. Comparing base (2674f6d) to head (6222d75).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1199      +/-   ##
==========================================
- Coverage   86.58%   86.57%   -0.02%     
==========================================
  Files          95       95              
  Lines        8586     8586              
  Branches      719      719              
==========================================
- Hits         7434     7433       -1     
  Misses        883      883              
- Partials      269      270       +1     

Flag	Coverage Δ
unittests	86.57% <ø> (-0.02%)	⬇️

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

Files	Coverage Δ
...roller/test/test_ackermann_steering_controller.cpp	100.00% <ø> (ø)
...roller/test/test_ackermann_steering_controller.hpp	86.59% <ø> (ø)
.../test_ackermann_steering_controller_preceeding.cpp	100.00% <ø> (ø)
.../include/admittance_controller/admittance_rule.hpp	100.00% <ø> (ø)
...ude/admittance_controller/admittance_rule_impl.hpp	93.51% <ø> (ø)
...dmittance_controller/src/admittance_controller.cpp	73.98% <ø> (ø)
...nce_controller/test/test_admittance_controller.cpp	100.00% <ø> (ø)
...nce_controller/test/test_admittance_controller.hpp	94.79% <ø> (ø)
...ntroller/test/test_bicycle_steering_controller.cpp	100.00% <ø> (ø)
...ntroller/test/test_bicycle_steering_controller.hpp	83.11% <ø> (ø)
... and 43 more

... and 1 file with indirect coverage changes