Add --without-cache option to tests

[sneakers-the-rat]

Fix: #1305
Fix: #1297

The tests can be run in parallel, except for tests which make network requests because the requests cache isn't designed for it. we should have an option to disable it anyway.

The odd yield; return; pattern is because if there is any yield statement in the function, pytest expects it to yield something, so we yield nothing and then have no cleanup stage when --without-cache is passed

tests can then be run in parallel like:

pip install pytest-xdist
pytest -n auto --without-cache

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.34%. Comparing base (bdabda1) to head (5556007).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2051   +/-   ##
=======================================
  Coverage   80.34%   80.34%           
=======================================
  Files         107      107           
  Lines       11967    11967           
  Branches     3418     3418           
=======================================
  Hits         9615     9615           
  Misses       1783     1783           
  Partials      569      569           

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