Add more products to fci_l2_nc reader

[strandgren]

This PR adds some more products to the fci_l2_nc reader. It also makes the file_patterns in the yaml-file less stringent in order to be compatible with L2 files from different processing environments.

The PR is mostly about adding new product entries entries in the yaml-file, but also include some minor changes in the py-file in order to allow both the CRM and OCA products to use the _slice_dataset method, initially developed for the multi-dimensional segmented ASR product.

• Make file_patterns less stringent.
• Add FIR product
• Add OLR product
• Add CRM product

[codecov]

Codecov Report

Merging #2102 (fddcaad) into main (56eb21b) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2102      +/-   ##
==========================================
- Coverage   93.92%   93.92%   -0.01%     
==========================================
  Files         283      283              
  Lines       42715    42714       -1     
==========================================
- Hits        40120    40119       -1     
  Misses       2595     2595              

Flag	Coverage Δ
behaviourtests	4.71% <0.00%> (+<0.01%)	⬆️
unittests	94.48% <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/fci_l2_nc.py	99.45% <100.00%> (-0.01%)	⬇️

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[coveralls]

Coverage decreased (-0.0001%) to 94.421% when pulling fddcaad on strandgren:add_more_fci_l2_products into 56eb21b on pytroll:main.

[strandgren]

Coverage tests are most likely failing because some lines of tested code have been removed.

[mraspaud]

LGTM!