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8078b8f3 - Change ATEN generator argument type to const std::optional<Generator>& (#6686)

Change ATEN generator argument type to const std::optional<Generator>& (#6686) Co-authored-by: cyy <cyyever@outlook.com> Summary: To adopt the changes in pytorch/pytorch#120076 To be noted, the original author is @cyyever and this is copied from #6595 Test Plan: CI