legacy: Arduino preprocess subroutine refactorization (part 4)

[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?

This PR is a try to split the bigger PR #2147 into smaller pieces to allow an easier review process.

What is the current behavior?

No changes

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

No

Other information

[codecov]

Codecov Report

Patch coverage: 72.85% and project coverage change: -0.02 ⚠️

Comparison is base (9ce2904) 62.78% compared to head (37c34b2) 62.77%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2194      +/-   ##
==========================================
- Coverage   62.78%   62.77%   -0.02%     
==========================================
  Files         221      221              
  Lines       19465    19475      +10     
==========================================
+ Hits        12222    12225       +3     
- Misses       6154     6162       +8     
+ Partials     1089     1088       -1     

Flag	Coverage Δ
unit	62.77% <72.85%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
legacy/builder/ctags/ctags_to_prototypes.go	89.06% <ø> (+4.21%)	⬆️
legacy/builder/preprocess_sketch.go	0.00% <0.00%> (ø)
legacy/builder/container_find_includes.go	70.28% <54.54%> (-0.92%)	⬇️
arduino/builder/preprocessor/gcc.go	79.06% <79.06%> (ø)
legacy/builder/container_add_prototypes.go	75.86% <100.00%> (+0.86%)	⬆️
legacy/builder/ctags/ctags_has_issues.go	98.58% <100.00%> (-0.04%)	⬇️
legacy/builder/ctags/ctags_parser.go	98.01% <100.00%> (+0.01%)	⬆️
legacy/builder/prototypes_adder.go	89.83% <100.00%> (-0.50%)	⬇️

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