feat: Move test formatter from .github/workflows/format_diff.py to python-gardenlinux-lib

[Leon-hk]

What this PR does / why we need it:

• For the still unmerged reproducibility checker, I've written a format_diff.py script which generates a readme report for the workflow run
• This script manually parsed the flavors directory and created feature trees. But this can also be way easier and more reliable done using the python-gardenlinux-lib
• This PR ports the readme generator to the python-gardenlinux-lib in order to clean up the workflows directory, to use features of the library and to be able to test the output with simple unit tests

[codecov]

Codecov Report

❌ Patch coverage is 95.37954% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.41%. Comparing base (a776256) to head (7b89b74).
⚠️ Report is 31 commits behind head on main.

Files with missing lines	Patch %	Lines
...gardenlinux/features/reproducibility/comparator.py	89.39%	7 Missing ⚠️
...c/gardenlinux/features/reproducibility/__main__.py	89.58%	5 Missing ⚠️
...ardenlinux/features/reproducibility/diff_parser.py	98.68%	1 Missing ⚠️
...nux/features/reproducibility/markdown_formatter.py	99.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #294      +/-   ##
==========================================
- Coverage   91.51%   91.41%   -0.11%     
==========================================
  Files          42       49       +7     
  Lines        2158     2585     +427     
==========================================
+ Hits         1975     2363     +388     
- Misses        183      222      +39     

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[Leon-hk]

Thanks for your detailed feedback. I have heavily restricted the formatter and implemented all your comments. It's still a massive PR, as it also contains the difference generator now. So take your time!

I was not able to find a python package or better way to unpack .oci containers, so I've implemented unpacking logic myself. It works so far.

[NotTheEvilOne]

In general this is a nice feature. I'm not sure if gl-diff is the most suitable command line tool name for it. As you compare OCI images or tar files based on features you may want to name it something similar to gl-feature-fs-diff?

[Leon-hk]

Thanks for your valuable feedback, I tried to clean things up as much as possible

[NotTheEvilOne]

One note left, otherwise looks good. Great work.

[NotTheEvilOne]

Here you can also use a template for at least part of the generated content.

[Leon-hk]

I've extended the template scope to also include the run number