[ET-VK][ez] Add print operator for `StorageType` enum

## Context

As title. Add a long overdue print operator for the `StorageType` enum, similar to the one that already exists for the `GPUMemoryLayout` enum.

Differential Revision: [D68237420](https://our.internmc.facebook.com/intern/diff/D68237420/)

ghstack-source-id: 261607000
Pull Request resolved: https://github.com/pytorch/executorch/pull/7685

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