Pants CI: Run all unit and pack tests #1434

Job	Run time
Pack Tests (pants runs: pytest) - Python 3.8	2m 3s
Pants Plugins Tests (pants runs: pytest) - Python 3.9	2m 31s
Pack Tests (pants runs: pytest) - Python 3.9	1m 40s
Unit Tests Shard 0/4 (pants runs: pytest) - Python 3.8	3m 24s
Unit Tests Shard 1/4 (pants runs: pytest) - Python 3.8	3m 49s
Unit Tests Shard 2/4 (pants runs: pytest) - Python 3.8	4m 48s
Unit Tests Shard 3/4 (pants runs: pytest) - Python 3.8	4m 12s
Unit Tests Shard 0/4 (pants runs: pytest) - Python 3.9	2m 38s
Unit Tests Shard 1/4 (pants runs: pytest) - Python 3.9	3m 6s
Unit Tests Shard 2/4 (pants runs: pytest) - Python 3.9	3m 30s
Unit Tests Shard 3/4 (pants runs: pytest) - Python 3.9	3m 57s
Set Merge OK (Tests)	1s
Merge OK (Tests)	1s
	35m 40s

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