SFN: Flatten source tree to reduce change of hitting the MAX_PATH in Windows

[bblommers]

Fixes #7536

[codecov]

Codecov Report

Attention: Patch coverage is 98.59155% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 94.07%. Comparing base (9aef694) to head (e3e44eb).
Report is 151 commits behind head on master.

Files	Patch %	Lines
...resource_output_transformer/transformer_factory.py	70.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7550      +/-   ##
==========================================
- Coverage   95.88%   94.07%   -1.82%     
==========================================
  Files         843     1070     +227     
  Lines       82578    91825    +9247     
==========================================
+ Hits        79178    86381    +7203     
- Misses       3400     5444    +2044     

Flag	Coverage Δ
servertests	29.57% <0.00%> (-2.96%)	⬇️
unittests	94.04% <98.59%> (-1.81%)	⬇️

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[github-actions]

This is now part of moto >= 5.0.5.dev13