Fix Deadlock with parallel stop-world/fork calls in MT #12561

Job	Run time
check_format	1m 43s
x86_64-gnu-test (1.7.3)	35m 2s
x86_64-gnu-test (1.8.2)	35m 8s
x86_64-gnu-test-preview_mt	5m 54s
x86_64-gnu-test (1.9.2)	34m 22s
x86_64-gnu-test (1.10.1)	35m 9s
x86_64-musl-test	38m 25s
x86_64-gnu-test (1.11.2)	35m 29s
x86_64-gnu-test (1.12.2)	35m 27s
x86_64-gnu-test (1.13.3)	35m 52s
x86_64-gnu-test (1.14.0)	33m 54s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	36m 10s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	34m 45s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	33m 50s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	36m 28s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	35m 31s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	35m 11s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	33m 24s
	9h 31m 44s

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