improve filter/ignore warnings

[avaldebe]

• ignore DeprecationWarning and FutureWarning raised outside pyaerocom
• remove ignore_warnings apply option
• ignore specific geonum and iris warnings on tests,
  instead using ignore_warnings to capture and ingore
  each trigger
• remove const.FILTER_IRIS_WARNINGS

[codecov]

Codecov Report

Merging #552 (0d23f02) into main-dev (9911d3f) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           main-dev     #552      +/-   ##
============================================
- Coverage     76.98%   76.96%   -0.02%     
============================================
  Files            97       97              
  Lines         17509    17496      -13     
============================================
- Hits          13479    13466      -13     
  Misses         4030     4030              

Flag	Coverage Δ
unittests	76.96% <100.00%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
pyaerocom/config.py	83.39% <ø> (-0.04%)	⬇️
pyaerocom/io/iris_io.py	94.61% <ø> (-0.05%)	⬇️
pyaerocom/_lowlevel_helpers.py	82.48% <100.00%> (ø)
pyaerocom/_warnings.py	88.88% <100.00%> (ø)
pyaerocom/aeroval/coldatatojson_helpers.py	71.87% <100.00%> (ø)
pyaerocom/griddeddata.py	61.38% <100.00%> (-0.04%)	⬇️
pyaerocom/io/read_ebas.py	88.08% <100.00%> (-0.05%)	⬇️
pyaerocom/mathutils.py	81.48% <100.00%> (ø)
pyaerocom/plot/mapping.py	96.52% <100.00%> (ø)
pyaerocom/plot/plotscatter.py	100.00% <100.00%> (ø)
... and 1 more

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