Add unit tests for slice utils

[GautamBytes]

This PR adds unit tests for the FilterHttpRouteMatch function in pkg/util/slices_utils.go.

The tests verify the filtering logic against various scenarios, including matching by headers and paths, ensuring the function behaves as expected and preventing future regressions.

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[GautamBytes]

@hantmac please review it whenever feasible!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.59%. Comparing base (00aae12) to head (2cde12e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #290      +/-   ##
==========================================
+ Coverage   47.52%   47.59%   +0.07%     
==========================================
  Files          63       63              
  Lines        9799     9799              
==========================================
+ Hits         4657     4664       +7     
+ Misses       4585     4578       -7     
  Partials      557      557              

Flag	Coverage Δ
unittests	47.59% <ø> (+0.07%)	⬆️

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[GautamBytes]

#288 (comment)
same here !