Update AVHRR EPS reader to read cloud flags information

[fwfichtner]

• Closes Update AVHRR EPS reader to read cloud flags information #2638
• Tests added
• Fully documented
• Add your name to AUTHORS.md if not there already

[fwfichtner]

We can take care of the CI problems if this is something you'd be interested to merge.

[djhoese]

You mentioned in your issue that you're using an old version of Satpy. Does that mean that this functionality and variable used to work, but was removed?

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (6fb1d1e) 95.20% compared to head (4181504) 95.22%.
Report is 45 commits behind head on main.

Files	Patch %	Lines
satpy/readers/eps_l1b.py	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2639      +/-   ##
==========================================
+ Coverage   95.20%   95.22%   +0.02%     
==========================================
  Files         354      356       +2     
  Lines       51370    51547     +177     
==========================================
+ Hits        48908    49088     +180     
+ Misses       2462     2459       -3     

Flag	Coverage Δ
behaviourtests	4.22% <0.00%> (-0.02%)	⬇️
unittests	95.85% <96.29%> (+0.02%)	⬆️

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[coveralls]

Pull Request Test Coverage Report for Build 6906945466

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 26 of 27 (96.3%) changed or added relevant lines in 2 files are covered.
• 12 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.02%) to 95.803%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
satpy/readers/eps_l1b.py	19	20	95.0%

Files with Coverage Reduction	New Missed Lines	%
satpy/tests/modifier_tests/test_angles.py	1	99.5%
satpy/modifiers/angles.py	2	99.22%
satpy/readers/nwcsaf_nc.py	4	82.21%
satpy/tests/reader_tests/modis_tests/_modis_fixtures.py	5	98.23%

Totals
Change from base Build 6847297703:	0.02%
Covered Lines:	49214
Relevant Lines:	51370

---

💛 - Coveralls

[fwfichtner]

Does that mean that this functionality and variable used to work, but was removed?

No, AFAIK this functionality was never there. We just forked, added this and then forgot about it.

[djhoese]

Ah ok, great. We'd really like a unit test to test this new variable. Thanks.

[djhoese]

pre-commit.ci autofix

[djhoese]

Thanks @fwfichtner. I did some refactoring of the code to make some of our checkers happy. It wasn't that your code was bad in anyway, just that your code being added tipped the scale for our checkers and revealed that the code was too complex. It is a little "cleaner" now.

I'll merge this when CI tests pass.