Add differential testing harness #423

Job	Run time
Lint	5m 51s
Test (ubuntu-24.04, aarch64-linux-android, x86_64-unknown-linux-gnu)	9m 0s
Test (ubuntu-24.04, x86_64-unknown-linux-gnu)	25m 37s
Test (macOS-latest, x86_64-apple-darwin)	20m 21s
cargo-deny	1m 2s
Test (windows-2022, x86_64-pc-windows-msvc)	43m 23s
test_success	3s
	1h 45m 17s

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