[Vulkan] Fix 64-bit I/O in Vulkan Delegate

[SS-JIA]

🐛 Describe the bug

Context

During export, the Vulkan delegate will downcast int64 and float64 tensors to int32 and int32 since 64-bit types are cumbersome to handle in compute shaders. However, this produces an issue the inputs and outputs of a model are 64-bit types; the ExecuTorch runtime will still be expecting to receive 64-bit data, but under the hood Vulkan will be treating the inputs and outputs as 32-bit.

Fixing

• Add a mechanism to allow the Vulkan delegate to automatically convert data to/from the source/destination ETensor type during input and output.

Versions

N/A

cc @manuelcandales @cbilgin