[vulkan] safe_downcast for buck build (#56540)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56540
Test Plan: Imported from OSS
Reviewed By: SS-JIA
Differential Revision: D27894423
Pulled By: IvanKobzarev
fbshipit-source-id: 2302f9ef9d06c2e072a5e83ea7abecf754ce325d
