legacy: removing a lot of duplicated/dead code

[cmaglie]

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• The PR has no duplicates (please search among the Pull Requests
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• The PR follows
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• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)
• configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

Some refactorings of the legacy builder (a lot of code duplication removed).

What is the current behavior?

No changes

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: 38.58% and project coverage change: +0.27% 🎉

Comparison is base (a47e35f) 63.06% compared to head (22dcc9e) 63.33%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2282      +/-   ##
==========================================
+ Coverage   63.06%   63.33%   +0.27%     
==========================================
  Files         221      219       -2     
  Lines       19771    19536     -235     
==========================================
- Hits        12469    12374      -95     
+ Misses       6195     6078     -117     
+ Partials     1107     1084      -23     

Flag	Coverage Δ
unit	63.33% <38.58%> (+0.27%)	⬆️

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

Files Changed	Coverage Δ
legacy/builder/create_cmake_rule.go	8.30% <6.14%> (-0.79%)	⬇️
legacy/builder/test/helper_tools_downloader.go	60.80% <16.66%> (+5.17%)	⬆️
...der/wipeout_build_path_if_build_options_changed.go	78.84% <40.00%> (-5.16%)	⬇️
legacy/builder/phases/core_builder.go	71.55% <69.56%> (-2.74%)	⬇️
legacy/builder/builder_utils/utils.go	72.03% <71.42%> (+2.09%)	⬆️
legacy/builder/container_find_includes.go	71.52% <71.42%> (-0.41%)	⬇️
legacy/builder/types/types.go	85.71% <88.00%> (+5.71%)	⬆️
legacy/builder/utils/utils.go	89.24% <100.00%> (+43.32%)	⬆️

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