[ET-VK][AOT][ez] Introduce vulkan export utils lib (#6605)

Pull Request resolved: https://github.com/pytorch/executorch/pull/6600

## Changes

As title. Introduce a common Python utility library for scripts in the Vulkan backend.
ghstack-source-id: 251223077

Differential Revision: [D65291064](https://our.internmc.facebook.com/intern/diff/D65291064/)

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Co-authored-by: Stephen Jia <ssjia@meta.com>