refactor: replace experimental libraries with their std versions

[G-Rath]

These became stable in Go v1.21, so we can stop using the x/exp versions

(this will be enforced by the expotostd linter which is being introduced in the next version of golanglint-ci)

[cuixq]

@G-Rath I think some tests break due to this change - can you help to fix?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.71429% with 3 lines in your changes missing coverage. Please review.

Project coverage is 68.75%. Comparing base (e2eb458) to head (22a42de).

Files with missing lines	Patch %	Lines
cmd/osv-scanner/fix/state-relock-result.go	0.00%	2 Missing ⚠️
scripts/generate_mock_resolution_universe/main.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1620   +/-   ##
=======================================
  Coverage   68.74%   68.75%           
=======================================
  Files         200      200           
  Lines       19147    19150    +3     
=======================================
+ Hits        13163    13166    +3     
  Misses       5280     5280           
  Partials      704      704           

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