Enable sweep thread when calling GC.start #12889

Job	Run time
Windows 2022/Visual C++ 2022 (check)	3m 44s
Windows 2025/Visual C++ 2022 (check)	4m 23s
Windows 11-arm/Visual C++ (btest test-basic test-tool)	6m 28s
Windows 2025/Visual C++ 2022 (test-bundled-gems)	4m 19s
Windows result	4s
	18m 58s

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