refactor: use slices from standard library

[davidkuridza]

I noticed golang.org/x/exp/slices was updated by Renovate in one of our pipelines. This PR removes the dependency in favor of the slices package from the standard library.

The same can be done withgolang.org/x/exp/maps by adding Keys() and Values() to xmaps. Please let me know if I should do that as well.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.92%. Comparing base (99f5080) to head (12fe015).
Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1286      +/-   ##
==========================================
+ Coverage   73.90%   73.92%   +0.01%     
==========================================
  Files         189      189              
  Lines       12855    12855              
==========================================
+ Hits         9501     9503       +2     
+ Misses       2805     2804       -1     
+ Partials      549      548       -1     

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