Tests

Respect gitignore #1118

Job	Run time
cargo-mutants	1h 17m 12s
incremental-mutants	6m 0s
build (macOS-latest, stable)	1m 11s
build (macOS-latest, nightly)	1m 13s
build (macOS-latest, 1.70)	1m 16s
build (ubuntu-latest, stable)	1m 17s
build (ubuntu-latest, nightly)	1m 16s
build (ubuntu-latest, 1.70)	1m 18s
build (windows-latest, stable)	1m 3s
build (windows-latest, nightly)	1m 4s
build (windows-latest, 1.70)	1m 0s
	1h 33m 50s

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