test

Bump actions/cache from 2 to 4 #237

Job	Run time
Verify benchmarks compile	29s
Check it compiles on old Rust (1.31.0)	3m 23s
Run the big ignored tests	42s
32bit tests	27s
Check documentation links	14s
Clippy lints	7s
Miri checks	6m 11s
Check formatting	6s
Check it compiles on old Rust (1.45.0)	10s
Build & test (ubuntu-latest, stable)	22s
Build & test (ubuntu-latest, beta)	26s
Thread Sanitizer checks MacOS	6m 57s
Build & test (ubuntu-latest, nightly)	21s
Build & test (macos-latest, stable)	30s
Build & test (macos-latest, beta)	47s
Build & test (macos-latest, nightly)	34s
Build & test (windows-latest, stable)	2m 14s
Build & test (windows-latest, beta)	58s
Build & test (windows-latest, nightly)	1m 5s
	26m 3s

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