[vulkan] 2D prepacking for conv2d (#48816)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/48816
Test Plan: Imported from OSS
Reviewed By: AshkanAliabadi
Differential Revision: D25786280
Pulled By: SS-JIA
fbshipit-source-id: b41bf55dcff8f3dfbbf1994171e2ef62f16ff29a
