Fix resolve python interpreter when frozen

[ptsavol]

Always use embedded Python as default when frozen and on Windows. We cannot search python from the PATH because %USERPROFILE%/AppData/Local/Microsoft/WindowsApps/ is in PATH by default on all users and this dir contains a python.exe that either opens the Microsoft Store or opens the Python that was downloaded from the Microsoft Store.

Fixes spine-tools/Spine-Toolbox#2823

Checklist before merging

• Unit tests have been added/updated accordingly
• Code has been formatted by black
• Unit tests pass

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 62.69%. Comparing base (a2d2c42) to head (56321f5).

Files	Patch %	Lines
spine_engine/utils/helpers.py	0.00%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #143      +/-   ##
==========================================
+ Coverage   62.55%   62.69%   +0.13%     
==========================================
  Files          40       40              
  Lines        3848     3849       +1     
  Branches      766      767       +1     
==========================================
+ Hits         2407     2413       +6     
+ Misses       1293     1288       -5     
  Partials      148      148              

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