Handle cross-thread slab frees #487

Job	Run time
security / security-static	30s
lint / lint	4m 54s
security / codeql-gate	37m 8s
security / license-gate	2m 42s
test / setup-matrix	3s
test / test-windows (windows-latest, CLANG64, x86_64)	41m 10s
test / test-unix (macos-15-intel, cc, c++)	32m 9s
test / test-unix (ubuntu-latest, gcc, g++)	18m 2s
test / test-unix (ubuntu-24.04-arm, gcc, g++)	1h 17m 22s
test / test-unix (macos-14, cc, c++)	15m 44s
ci-ok	2s
	3h 49m 46s

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