audit: add getters for SCMs, Files and variantId

[rhubert]

Needed for sbom from audit generation

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.24%. Comparing base (ca1f5e7) to head (6cdb975).
⚠️ Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
pym/bob/audit.py	50.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #700      +/-   ##
==========================================
- Coverage   89.25%   89.24%   -0.02%     
==========================================
  Files          50       50              
  Lines       16446    16452       +6     
==========================================
+ Hits        14679    14682       +3     
- Misses       1767     1770       +3     

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[jkloetzke]

The Audit classes are not part of the public plugin API. Actually, only the classes named in the documentation should be used by plugins.

So if we expose the Audit class it would have to be added to the documentation at least. But I'm not sure we should really do this. It's only a thin wrapper around the JSON data. I guess there isn't too much value to use it, is it?