fix: allow lib-install from git using revision hash as a reference

[cmaglie]

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• Tests for the changes have been added (for bug fixes / features)
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What kind of change does this PR introduce?

A previous "fix" allowed the installation of a library from git by specifying a branch, but introduced a regression, making it impossible to install from git by specifying a revision hash.

What is the current behavior?

A library can not be installed from git using a revision hash, see #2860 for details

What is the new behavior?

It is now allowed to install from git using a revision hash.

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

Other information

Fix #2860

[codecov]

Codecov Report

Attention: Patch coverage is 36.84211% with 12 lines in your changes missing coverage. Please review.

Project coverage is 67.82%. Comparing base (00a33b7) to head (39aca21).

Files with missing lines	Patch %	Lines
...rnal/arduino/libraries/librariesmanager/install.go	36.84%	6 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2882      +/-   ##
==========================================
- Coverage   67.88%   67.82%   -0.06%     
==========================================
  Files         238      238              
  Lines       22410    22418       +8     
==========================================
- Hits        15212    15205       -7     
- Misses       6004     6012       +8     
- Partials     1194     1201       +7     

Flag	Coverage Δ
unit	67.82% <36.84%> (-0.06%)	⬇️

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