[ENH] move utils module to folder

[fkiraly]

This is a minimal refactor preparatory PR.

It changes the utils module from a file to a folder, in anticipation of other PR that may add further utils - to avoid that everyone works on the same file.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.77%. Comparing base (99928f8) to head (0069e78).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1612      +/-   ##
==========================================
+ Coverage   52.75%   52.77%   +0.02%     
==========================================
  Files          36       37       +1     
  Lines        4333     4335       +2     
==========================================
+ Hits         2286     2288       +2     
  Misses       2047     2047              

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