Handle cross-thread slab frees #416

Job	Run time
lint / lint	5m 22s
security / codeql-gate	45m 46s
security / security-static	32s
security / license-gate	2m 57s
test / setup-matrix	3s
test / test-unix (ubuntu-latest, gcc, g++)	14m 48s
test / test-unix (macos-15-intel, cc, c++)	23m 13s
test / test-windows (windows-latest, CLANG64, x86_64)	34m 36s
test / test-unix (ubuntu-24.04-arm, gcc, g++)	1h 9m 15s
test / test-unix (macos-14, cc, c++)	12m 32s
ci-ok	4s
	3h 29m 8s

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