Pants: Add BUILD metadata for integration tests (#6275) #1559

Job	Run time
Pants Plugins Tests (pants runs: pytest) - Python 3.9	4m 8s
Pack Tests (pants runs: pytest) - Python 3.8	3m 4s
Pack Tests (pants runs: pytest) - Python 3.9	3m 24s
Unit Tests Shard 0/4 (pants runs: pytest) - Python 3.8	4m 45s
Unit Tests Shard 1/4 (pants runs: pytest) - Python 3.8	5m 16s
Unit Tests Shard 2/4 (pants runs: pytest) - Python 3.8	5m 11s
Unit Tests Shard 3/4 (pants runs: pytest) - Python 3.8	5m 18s
Unit Tests Shard 0/4 (pants runs: pytest) - Python 3.9	4m 35s
Unit Tests Shard 1/4 (pants runs: pytest) - Python 3.9	5m 32s
Unit Tests Shard 2/4 (pants runs: pytest) - Python 3.9	5m 10s
Unit Tests Shard 3/4 (pants runs: pytest) - Python 3.9	5m 27s
Set Merge OK (Tests)	1s
Merge OK (Tests)	1s
	51m 52s

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