Autoload encodings on the main ractor #679

Job	Run time
Windows 2025/Visual C++ 2022 (check)	53m 1s
Windows 2025/Visual C++ 2022 (test-bundled-gems)	52m 6s
Windows 2022/Visual C++ 2019 (check)	46m 15s
Windows 11-arm/Visual C++ (btest test-basic test-tool)	1h 3m 38s
Windows result	2s
	3h 35m 2s

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