Reuse benchmark threads across runs #179

Job	Run time
Clippy (ubuntu-latest)	22s
Unit Test (ubuntu-latest, stable)	38s
Clippy (macos-latest)	36s
Examples Bench (ubuntu-latest)	2m 18s
Unit Test (ubuntu-latest, nightly-2024-02-10)	38s
Clippy (windows-latest)	49s
Examples Test (ubuntu-latest, stable)	50s
Examples Bench (macos-latest)	5m 23s
Unit Test (macos-latest, stable)	49s
Examples Test (ubuntu-latest, nightly-2024-02-10)	43s
Examples Bench (windows-latest)	3m 33s
Unit Test (macos-latest, nightly-2024-02-10)	1m 23s
Examples Test (macos-latest, stable)	1m 11s
Unit Test (windows-latest, stable)	1m 14s
Internals Bench (ubuntu-latest)	18s
Examples Test (macos-latest, nightly-2024-02-10)	1m 15s
Unit Test (windows-latest, nightly-2024-02-10)	1m 13s
Internals Bench (macos-latest)	35s
Rustdoc	15s
Examples Test (windows-latest, stable)	1m 33s
Internals Bench (windows-latest)	1m 3s
Examples Test (windows-latest, nightly-2024-02-10)	1m 18s
Rustfmt	12s
Unit Test (Miri)	1m 13s
	29m 22s

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