Disabled FITS & UnitsWarnings by default for ESASky module

[imbasimba]

As suggested by @bsipocz here, some warnings are not useful to the users. Thus, the suggested warning as well as some extra warnings are now disabled by default, but can be enabled via the verbose parameter.

Also, some minor pep8 formatting.

[codecov[bot]]

Codecov Report

Merging #2550 (3409715) into main (b0d9f5f) will decrease coverage by 0.01%. The diff coverage is 19.23%.

@@            Coverage Diff             @@
##             main    #2550      +/-   ##
==========================================
- Coverage   63.99%   63.97%   -0.02%     
==========================================
  Files         132      132              
  Lines       16969    16984      +15     
==========================================
+ Hits        10859    10866       +7     
- Misses       6110     6118       +8     

Impacted Files	Coverage Δ
astroquery/esasky/core.py	18.37% <19.23%> (-0.04%)	:arrow_down:
astroquery/cadc/core.py	81.18% <0.00%> (+0.95%)	:arrow_up:

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