Add support for GK-2B/GOCI2 data at L1b/c

[simonrp84]

This PR adds support for level 1 data produced by the GOCI-II ocean color instrument flying aboard GeoKompsat-2A.

Data is produced by the sensor in a series of sections that, together, cover either an area around Korea or the full disk. Each section is sensed at a different time. There is also a data product joining these sections together to create a full-area image at L1c.

Right now, this PR is a draft as:

1. I haven't added any tests
2. The full disk data is not read successfully.
3. I need to add a proper area definition, which should be possible from the L1 attributes (the data is in GEOS projection). Currently I cannibalised code from the L2 GOCI reader that generates a swathdefinition.

• Tests added
• Fully documented

[simonrp84]

pre-commit.ci autofix

[codecov]

Codecov Report

Attention: Patch coverage is 27.86885% with 44 lines in your changes are missing coverage. Please review.

Project coverage is 95.85%. Comparing base (c9aabb7) to head (d5113c8).
Report is 3 commits behind head on main.

❗ Current head d5113c8 differs from pull request most recent head 6527d45. Consider uploading reports for the commit 6527d45 to get more accurate results

Files	Patch %	Lines
satpy/readers/goci2_l1_nc.py	27.86%	44 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2796      +/-   ##
==========================================
- Coverage   95.95%   95.85%   -0.10%     
==========================================
  Files         379      380       +1     
  Lines       53861    53922      +61     
==========================================
+ Hits        51680    51686       +6     
- Misses       2181     2236      +55     

Flag	Coverage Δ
behaviourtests	4.08% <0.00%> (-0.01%)	⬇️
unittests	95.94% <27.86%> (-0.10%)	⬇️

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