Cleanup hy2 reader

[TAlonglong]

Clean up hy2 reader to preserve the attribute over when scaling and masking. This to keep the rename of the attribute with space valid range to valid_range

The previous tests did not catch this because the the renaming of the valid range attribute happened int the test environment as a reference. However in real data files this was to progressed.

To simulate this I made a override of __getitem__ to make a copy of the data instead of a reference.

This was done in the PR #2211, but badly messed up. This is a diff from that branch witch is applied here. Hope this is not to bad.

• Closes hy2_scat_l2b_h5 reader does not work any more due to space in valid range attribute #2208
• Tests added
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

Merging #2268 (004d910) into main (6081a02) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2268   +/-   ##
=======================================
  Coverage   94.25%   94.25%           
=======================================
  Files         300      300           
  Lines       45649    45669   +20     
=======================================
+ Hits        43026    43046   +20     
  Misses       2623     2623           

Flag	Coverage Δ
behaviourtests	4.66% <0.00%> (-0.01%)	⬇️
unittests	94.90% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
satpy/readers/hy2_scat_l2b_h5.py	98.33% <100.00%> (+0.11%)	⬆️
satpy/tests/reader_tests/test_hy2_scat_l2b_h5.py	100.00% <100.00%> (ø)

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[coveralls]

Coverage increased (+0.002%) to 94.85% when pulling 004d910 on TAlonglong:issue2208-hy2-scat-l2b-h5-valid-range-cherrypick into 6081a02 on pytroll:main.

[mraspaud]

Thanks for the cleanup, LGTM!