chore(opossum): Prefer add functions when building collections

[sschuberth]

Avoid any confusion what this refers to for these (extension) functions.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 68.02%. Comparing base (6db8eae) to head (63db06b).

Files with missing lines	Patch %	Lines
...rc/main/kotlin/utils/SortedCollectionConverters.kt	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #9617   +/-   ##
=========================================
  Coverage     68.02%   68.02%           
  Complexity     1285     1285           
=========================================
  Files           249      249           
  Lines          8828     8828           
  Branches        921      921           
=========================================
  Hits           6005     6005           
  Misses         2433     2433           
  Partials        390      390           

Flag	Coverage Δ
funTest-docker	64.96% <ø> (ø)
test-ubuntu-24.04	35.80% <0.00%> (ø)
test-windows-2022	35.78% <0.00%> (ø)

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[sschuberth]

Merging despite the unrelated DownloaderFunTest failure.