Update Metimage reader for L2 test data

[pepephillips]

• This is essentially the L2 part to PR Update VII reader for test data v2 #1979 concerning the new METimage product format V4A (lat,lon instead of lon,lat)
• vii_l2_nc.yaml has been updated so L2 product readers accept the new lat/lon format and have the correct file pattern.
• test_vii_l2_nc.py has also been updated accordingly.

[codecov]

Codecov Report

Merging #2146 (e15d251) into main (bafe54e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2146   +/-   ##
=======================================
  Coverage   93.88%   93.88%           
=======================================
  Files         283      283           
  Lines       43093    43123   +30     
=======================================
+ Hits        40458    40488   +30     
  Misses       2635     2635           

Flag	Coverage Δ
behaviourtests	4.78% <0.00%> (-0.01%)	⬇️
unittests	94.54% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
satpy/tests/reader_tests/test_vii_l2_nc.py	100.00% <100.00%> (ø)
satpy/resample.py	79.56% <0.00%> (-0.34%)	⬇️
satpy/readers/utils.py	92.34% <0.00%> (ø)
satpy/tests/reader_tests/test_utils.py	100.00% <0.00%> (ø)
satpy/tests/reader_tests/test_modis_l2.py	100.00% <0.00%> (ø)
satpy/tests/reader_tests/test_gpm_imerg.py	100.00% <0.00%> (ø)
satpy/tests/reader_tests/test_modis_l1b.py	100.00% <0.00%> (ø)
satpy/tests/reader_tests/test_ahi_hsd.py	99.62% <0.00%> (+<0.01%)	⬆️
satpy/tests/reader_tests/_modis_fixtures.py	97.61% <0.00%> (+0.01%)	⬆️
satpy/readers/modis_l2.py	89.81% <0.00%> (+0.29%)	⬆️
... and 2 more

[coveralls]

Coverage remained the same at 94.484% when pulling e15d251 on pepephillips:L2_dev into 15dbf3d on pytroll:main.

[mraspaud]

LGTM, thanks for fixing the tests too!