Merge pystandalone crypt and fallback on python RNG

[twiggler]

This PR merges the logic in crypt.py of pystandalone with the mainline crypt.py.

Additionaly, when the pystandalone rng fails.
a fallback on the python cryptographic rng os.urandom is added

[codecov]

Codecov Report

Attention: Patch coverage is 52.38095% with 10 lines in your changes missing coverage. Please review.

Project coverage is 44.49%. Comparing base (c983d84) to head (25db239).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
acquire/crypt.py	52.38%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #221      +/-   ##
==========================================
- Coverage   44.51%   44.49%   -0.02%     
==========================================
  Files          26       26              
  Lines        3493     3508      +15     
==========================================
+ Hits         1555     1561       +6     
- Misses       1938     1947       +9     

Flag	Coverage Δ
unittests	44.49% <52.38%> (-0.02%)	⬇️

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