upgrade Pex to 2.2.1 (Cherry-pick of #20587) (#20652) #21877

Job	Run time
Ensure PR has a category label	3s
Classify changes	5s
Bootstrap Pants, test Rust (macOS11-x86_64)	20m 33s
Bootstrap Pants, test Rust (Linux-ARM64)	11m 29s
Bootstrap Pants, test and lint Rust (Linux-x86_64)	9m 14s
Build wheels (Linux-ARM64)	0s
Build wheels (Linux-x86_64)	0s
Build wheels (macOS10-15-x86_64)	0s
Build wheels (macOS11-ARM64)	0s
Lint Python and Shell	2m 47s
Test Python (Linux-x86_64) Shard 2/10	15m 47s
Test Python (Linux-x86_64) Shard 0/10	17m 12s
Test Python (Linux-x86_64) Shard 1/10	13m 52s
Test Python (Linux-x86_64) Shard 3/10	15m 1s
Test Python (Linux-x86_64) Shard 4/10	24m 49s
Test Python (Linux-x86_64) Shard 5/10	11m 49s
Test Python (Linux-x86_64) Shard 6/10	9m 7s
Test Python (Linux-x86_64) Shard 7/10	15m 10s
Test Python (Linux-x86_64) Shard 8/10	12m 47s
Test Python (Linux-x86_64) Shard 9/10	12m 23s
Test Python (Linux-ARM64)	2m 42s
Test Python (macOS11-x86_64)	11m 40s
Set Merge OK	1s
Merge OK	1s
	3h 26m 32s

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