pex: switch to SCIE binary instead of PEX #25000

Job	Run time
Classify changes	3s
Bootstrap Pants, test Rust (macOS13-x86_64)	8m 55s
Bootstrap Pants, test Rust (Linux-ARM64)	6m 16s
Bootstrap Pants, test and lint Rust (Linux-x86_64)	5m 24s
Ensure PR has release notes	2s
Build wheels (Linux-ARM64)	0s
Build wheels (Linux-x86_64)	0s
Build wheels (macOS13-x86_64)	0s
Build wheels (macOS14-ARM64)	0s
Test Python (Linux-x86_64) Shard 0/10	17m 32s
Test Python (Linux-x86_64) Shard 2/10	18m 47s
Lint Python and Shell	3m 43s
Test Python (Linux-x86_64) Shard 1/10	17m 37s
Test Python (Linux-x86_64) Shard 3/10	14m 41s
Test Python (Linux-x86_64) Shard 4/10	51m 8s
Test Python (Linux-x86_64) Shard 5/10	13m 18s
Test Python (Linux-x86_64) Shard 6/10	9m 17s
Test Python (Linux-x86_64) Shard 7/10	17m 16s
Test Python (Linux-x86_64) Shard 8/10	16m 6s
Test Python (Linux-x86_64) Shard 9/10	10m 49s
Test Python (Linux-ARM64)	9m 26s
Test Python (macOS13-x86_64)	23m 35s
Set Merge OK	0s
Merge OK	1s
	4h 3m 56s

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