misc: add tests to utils.fs_supports_link_method and utils.convert_to…

[Bonifacio2]

…_datetime

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.10%. Comparing base (b22e40d) to head (8ef107e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3662      +/-   ##
==========================================
+ Coverage   86.07%   86.10%   +0.03%     
==========================================
  Files         119      119              
  Lines       12353    12353              
  Branches     2052     2052              
==========================================
+ Hits        10633    10637       +4     
+ Misses       1140     1138       -2     
+ Partials      580      578       -2     

Flag	Coverage Δ
unittests	85.97% <ø> (+0.03%)	⬆️

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