Add pytest-testmon plugin to speed up local testing

[lebrice]

Adds pytest-testmon as a dev dependency, makes testing super quick by only re-running tests that depend on code that changed since the last test run!

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.93%. Comparing base (9b4a7cd) to head (3d71ca5).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #125   +/-   ##
=======================================
  Coverage   72.93%   72.93%           
=======================================
  Files          15       15           
  Lines        2176     2176           
=======================================
  Hits         1587     1587           
  Misses        589      589           

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[satyaog]

We could want to still run all of the integration tests when releasing a new version. We could also want to periodically run integration tests on the remotes we support just in case something changes on their end which could break things on ours