Switch test runner from nosetest to pytest #5613

Job	Run time
Skip Duplicate Jobs Pre Job	4s
Self-check on Python 3.8 - Python 3.8	8m 46s
Unit Tests - Python 3.8	16m 28s
Lint Checks (black, flake8, etc.) - Python 3.8	3m 4s
Unit Tests - Python 3.9	16m 24s
Pack Tests - Python 3.8	3m 13s
Compile (pip deps, pylint, etc.) - Python 3.8	3m 53s
Integration Tests - Python 3.8	9m 17s
Lint Checks (black, flake8, etc.) - Python 3.9	2m 40s
Pack Tests - Python 3.9	2m 44s
Compile (pip deps, pylint, etc.) - Python 3.9	4m 16s
Integration Tests - Python 3.9	9m 6s
Slack notification for failed master builds	3s
	1h 19m 58s

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