Fix conversion script for v10 of METimage SRF

[ninahakansson]

Fix conversion script for v10 of METimage SRF, EPS-SGA1-METIMAGE_SRF_V10.nc

• Closes #xxxx
• Tests added
• Tests passed: Passes pytest pyspectral
• Passes flake8 pyspectral
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.17%. Comparing base (7a61fdf) to head (0c26413).
⚠️ Report is 16 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #295   +/-   ##
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  Coverage   91.17%   91.17%           
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  Files          25       25           
  Lines        2673     2674    +1     
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+ Hits         2437     2438    +1     
  Misses        236      236           

Flag	Coverage Δ
unittests	91.17% <ø> (+<0.01%)	⬆️

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[djhoese]

Are the values in the SRFs the same and this is just a group name change?

[Manny7717]

Quick verification notes on head 0c26413:

Verified locally: band-name parsing is sound - the script's band keys (e.g. vii_443, vii_865) parse via int(band.split("_")[-1]) to wavelengths in nm, and the three thresholds (wv>6000 -> LVWIR, >1000 -> SMWIR, else VISNIR) map every METimage band to the right family (probed all current BANDNAMES entries). The Instrument/ISRF/<family> paths are consistent with the v10 file's nested-group layout.

One compatibility question: the group-name change is unconditional, but the module docstring (lines 1-9) and rsr_convert_scripts/README.rst:201 still reference the plain EPS-SGA1_METIMAGE_SRF.nc (non-v10) file. If any users are still converting the older file (flat LVWIR/SMWIR/VISNIR groups), this change would break their conversion. Options: bump the docstring/README to point at the v10 file explicitly, or make the lookup tolerant (try nested path first, fall back to flat). Could not fetch the EUMETSAT file to double-check the exact v10 group names (anonymous sftp 404), so flagging rather than assuming.

Non-blocking - the fix itself looks correct for v10.

[adybbroe]

@djhoese SRFs have been improved. Especially the IR channels differ. Cannot really see any changes in the VIS/NIR bands. I faked @ninahakansson 's new SRFs as Metop-SG-A4 for the convenience of plotting them via:
python bin/composite_rsr_plot.py --platform_name Metop-SG-A1 Metop-SG-A4 --sensor metimage -r 8 14.0

[adybbroe]

Thanks for updating the SRFs to the latest from EUMETSAT!
LGTM