Include `FuseDequantLinearPass()` in `vulkan_preprocess` (#6168)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/6168

## Context

Include `FuseDequantLinearPass` as a part of `vulkan_preprocess`, so that fusing the quant/dequant nodes added by `VulkanQuantizer` can be done as part of the lowering process.
ghstack-source-id: 247613964
exported-using-ghexport

Reviewed By: jorgep31415

Differential Revision: D64249613

fbshipit-source-id: 6dbc88e0c062f8f9c41eeb09bf8ba02d9096d009