Optimize jobserver `try_acquire` #1420

Job	Run time	Billable time
Clippy	14s	0s
Test build-std (aarch64-tvos)	2m 43s	0s
Test CUDA support	46s	0s
Test build-std (aarch64-tvos-sim)	3m 50s	0s
Test build-std (x86_64-tvos)	2m 46s	0s
Rustfmt	10s	0s
MSRV (ubuntu-latest)	27s	0s
Test (stable)	34s	0s
MSRV (windows-latest)	36s	0s
Test (beta)	44s	0s
Test (nightly)	41s	0s
Test (linux32)	1m 18s	0s
Test (macos)	1m 29s	0s
Test (aarch64-macos)	54s	0s
Test (aarch64-ios)	1m 14s	0s
Test (win32)	1m 12s	0s
Test (win64)	1m 18s	0s
Test (mingw32)	1m 17s	0s
Test (mingw64)	1m 18s	0s
Test (windows-2019)	1m 18s	0s
Test (windows-aarch64, windows-latest, stable, aarch64-pc-windows-msvc, --no-run)	1m 15s	0s
Test (windows-clang, windows-2019, stable, x86_64-pc-windows-msvc, clang, clang++)	1m 20s	0s
Test (windows-clang-cl, windows-2019, stable, x86_64-pc-windows-msvc, clang-cl, clang-cl)	1m 17s	0s
	28m 41s	0s

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