legacy: some clean-ups of legacy code

[cmaglie]

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• Tests for the changes have been added (for bug fixes / features)
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• configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

Some cleanup on the legacy package

What is the current behavior?

What is the new behavior?

No changes

Does this PR introduce a breaking change, and is titled accordingly?

Other information

[codecov]

Codecov Report

Patch coverage: 63.63% and project coverage change: +0.09 🎉

Comparison is base (0b77c0a) 62.45% compared to head (75ac9d1) 62.54%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2160      +/-   ##
==========================================
+ Coverage   62.45%   62.54%   +0.09%     
==========================================
  Files         224      223       -1     
  Lines       19520    19467      -53     
==========================================
- Hits        12191    12176      -15     
+ Misses       6231     6196      -35     
+ Partials     1098     1095       -3     

Flag	Coverage Δ
unit	62.54% <63.63%> (+0.09%)	⬆️

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

Impacted Files	Coverage Δ
legacy/builder/create_cmake_rule.go	8.80% <0.00%> (ø)
legacy/builder/types/types.go	71.87% <ø> (+14.37%)	⬆️
legacy/builder/utils/utils.go	54.73% <0.00%> (-0.94%)	⬇️
legacy/builder/test/helper_tools_downloader.go	55.62% <100.00%> (ø)
legacy/builder/types/accessories.go	88.23% <100.00%> (+33.68%)	⬆️
...egacy/builder/unused_compiled_libraries_remover.go	76.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[alessio-perugini]

✂️ ✂️
I like the usage of golang.org/x/exp/slices 🤩