Unit tests for the new odometry implementation in diff_drive_controller

[vedh1234]

Fixes #2033

Description
This PR adds unit tests for the Odometry class in diff_drive_controller to verify the new mathematical logic introduced in #1854.

Changes

• Added test/test_odometry.cpp covering:
  • Exact Arc integration (Curved motion)
  • Linear and Pure Rotation motion
  • Open Loop updates
  • Handling of small dt
• Updated CMakeLists.txt to build the new test.

Testing

• Verified locally with colcon test: 8 tests passed, 0 failures.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.86%. Comparing base (272ac69) to head (0b246b1).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2099      +/-   ##
==========================================
+ Coverage   84.80%   84.86%   +0.06%     
==========================================
  Files         151      152       +1     
  Lines       14836    14859      +23     
  Branches     1286     1286              
==========================================
+ Hits        12581    12610      +29     
+ Misses       1784     1778       -6     
  Partials      471      471              

Flag	Coverage Δ
unittests	84.86% <100.00%> (+0.06%)	⬆️

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

Files with missing lines	Coverage Δ
diff_drive_controller/test/test_odometry.cpp	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[Amronos]

Thanks a lot for the tests! Some minor suggestions.

[christophfroehlich]

Thanks a lot, LGTM!