Switch test runner from nosetest to pytest #5611

Job	Run time
Skip Duplicate Jobs Pre Job	5s
Unit Tests - Python 3.8	16m 4s
Self-check on Python 3.8 - Python 3.8	9m 3s
Unit Tests - Python 3.9	16m 5s
Pack Tests - Python 3.8	2m 30s
Lint Checks (black, flake8, etc.) - Python 3.8	2m 58s
Integration Tests - Python 3.8	9m 6s
Compile (pip deps, pylint, etc.) - Python 3.8	3m 51s
Pack Tests - Python 3.9	2m 49s
Lint Checks (black, flake8, etc.) - Python 3.9	2m 47s
Integration Tests - Python 3.9	9m 21s
Compile (pip deps, pylint, etc.) - Python 3.9	4m 4s
Slack notification for failed master builds	5s
	1h 18m 48s

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