refactor(jtc): improve jtc tolerances

[thedevmystic]

Hello respected maintainers and reviewers!
This is Surya!

This PR addresses the following:

• Seperate declaration from definition for better compilation speed and readability.
• Refactor functions for better readability.
• Add new function (create_error_trajectory_point).
• Add extensive doxygen-style comments.
• Add tests for new function (create_error_trajectory_point).

---

1. If you have question, why I moved (or seperated) it to tolerances.cpp it is because the file was getting way too long for no reason. It would both increase compile time and future maintainance.

2. If you have question, why I added create_error_trajectory_point it is because we can calculate the current error point and then compare it with tolerances with ease!

---

A note: This is a continuation of the previous PR #2048 (closed now). Instead of doing new features (new tolerances option) and refactoring in one PR. I split them into 2 PRs one doing refactoring (current) and another future PR adding feature.

[codecov]

Codecov Report

❌ Patch coverage is 94.06780% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.90%. Comparing base (f72f813) to head (0fb8e41).

Files with missing lines	Patch %	Lines
...include/joint_trajectory_controller/tolerances.hpp	73.07%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2133      +/-   ##
==========================================
+ Coverage   84.79%   84.90%   +0.10%     
==========================================
  Files         151      152       +1     
  Lines       14833    14867      +34     
  Branches     1286     1292       +6     
==========================================
+ Hits        12578    12623      +45     
+ Misses       1784     1777       -7     
+ Partials      471      467       -4     

Flag	Coverage Δ
unittests	84.90% <94.06%> (+0.10%)	⬆️

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

Files with missing lines	Coverage Δ
joint_trajectory_controller/src/tolerances.cpp	100.00% <100.00%> (ø)
...int_trajectory_controller/test/test_tolerances.cpp	100.00% <100.00%> (ø)
...include/joint_trajectory_controller/tolerances.hpp	78.04% <73.07%> (-1.75%)	⬇️

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[thedevmystic]

Just dropping a comment since it's been 2 weeks with no follow ups :)