Add differential testing harness #285

Job	Run time
Test (ubuntu-20.04, x86_64-unknown-linux-gnu)	25m 26s
cargo-deny	2m 1s
Lint	7m 5s
Test (ubuntu-20.04, aarch64-linux-android, x86_64-unknown-linux-gnu)	9m 54s
Test (macOS-latest, x86_64-apple-darwin)	16m 30s
Test (windows-2022, x86_64-pc-windows-msvc)	44m 38s
test_success	4s
	1h 45m 38s

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