Vulkan memory allocator. (#42786)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/42786
Test Plan: Imported from OSS
Reviewed By: IvanKobzarev
Differential Revision: D23252332
Pulled By: AshkanAliabadi
fbshipit-source-id: 14e848ad81b4ba1367e8cf719343a51995457827
