support nested VM barrier synchronization #961

Job	Run time
Windows 2022/Visual C++ 2019 (check)	29m 24s
Windows 11-arm/Visual C++ (btest test-basic test-tool)	55m 1s
Windows 2022/Visual C++ 2019 (test-bundled-gems)	30m 30s
Windows 2025/Visual C++ 2019 (check)	27m 28s
Windows result	3s
	2h 22m 26s

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