Update CI and release pipelines to run unit and integration tests

[sedula27]

Update CI and release pipelines to run unit and integration tests

• Replace tox with pytest
• Run both unit and integration tests
• Remove test secrets from workflow env; integration tests use VCR playback mode against committed cassettes

[sedula27]

In playback mode, VCR matches outgoing requests against recorded ones by method + scheme + host + port + path + query (the default matcher set). If any of those don't match, VCR raises CannotOverwriteExistingCassetteException and the test fails. So updated to use the secrets from the repo with the same variables as the local env.test

https://vcrpy.readthedocs.io/en/latest/debugging.html

[rohit-joy]

@sedula27 Very good work!