LibCore: Port MappedFile to Windows #6548

Job	Run time
Lagom (macOS, macos-15, NO_FUZZ, Clang, false) / CI	27m 55s
Lagom (Linux, ubuntu-24.04, FUZZ, Clang, false) / CI	30m 21s
Lagom (Linux, ubuntu-24.04, NO_FUZZ, Clang, true) / CI	11m 57s
Lagom (Linux, ubuntu-24.04, NO_FUZZ, GNU, false) / CI	23m 32s
	1h 33m 45s

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