Change reader and component names from "VII" to "METimage" and fix minor issues

[ameraner]

This PR

• changes the name of the METimage instrument reader from vii_l1b_nc and vii_l2_nc to metimage_l1b_nc and metimage_l2_nc. The old reader names are put in deprecation (they still work but emit a FutureWarning). The python files and class names are adapted accordingly.
• The platform name is translated to the OSCAR names (Metop-SG-AX)
• With these fixes, the pyspectral RSR work correctly (from Add metimage average srf pyspectral#278 )

On top, two minor fixes are also implemented:

• the longitude arrays are wrapped to the -180, 180 range to avoid failures in resampling corner cases
• the yaml calibration configuration of one channel was faulty

... and the rows_per_scan attribute is added to datasets to support EWA resampling.

• Closes Rename VII readers and update VII readers for new test data #3202
• Tests added
• Fully documented

FYI @cesclc @TAlonglong @ludwigVonKoopa

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.32%. Comparing base (fbfbe21) to head (454a95a).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3395      +/-   ##
==========================================
- Coverage   96.32%   96.32%   -0.01%     
==========================================
  Files         466      464       -2     
  Lines       59096    59081      -15     
==========================================
- Hits        56922    56907      -15     
  Misses       2174     2174              

Flag	Coverage Δ
behaviourtests	3.59% <1.81%> (+<0.01%)	⬆️
unittests	96.40% <100.00%> (-0.01%)	⬇️

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