test: switch from deprecated optparse to argparse

[avivkeller]

optparse has been deprecated since Python 3.2 / 2.7, so we should upgrade to the currently maintained and recommended argparse. It's mostly a drop-in replacement.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.14%. Comparing base (535c2f7) to head (708bf68).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58224      +/-   ##
==========================================
+ Coverage   90.12%   90.14%   +0.02%     
==========================================
  Files         629      629              
  Lines      186638   186638              
  Branches    36618    36627       +9     
==========================================
+ Hits       168202   168241      +39     
+ Misses      11222    11207      -15     
+ Partials     7214     7190      -24     

see 26 files with indirect coverage changes

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