[ET-VK] Clean up api::vTensor class

[SS-JIA]

Stack from ghstack (oldest at bottom):

• [ET-VK] Introduce ParamsBindList to prevent needing to pass shared_ptr to bind parameter UBOs #3150
• -> [ET-VK] Clean up api::vTensor class #3149
• [ET-VK] Call destructor explicitly when move constructing Value #3148

Context

Now that we have forked the api/ directory from PyTorch Vulkan, we can clean up the vTensor class and remove functionality that is not necessary for the ExecuTorch Vulkan delegate.

The following changes are made:

• Remove unused member variables and member functions from vTensor and vTensorStorage
• Remove all quantization related member variables, member functions, and the vTensor constructor for quantized tensors. The Quantization API will be reworked from the ground up.
• Rename view_ (which is an instance of vTensorStorage) to storage_

Finally, the critical change that is introduced is that we now store storage_ as a direct vTensorStorage member variable in vTensor instead of storing it as a std::shared_ptr<vTensorStorage>.

For context, the reason storage_ was stored as a shared pointer is to be compliant with ATen Tensors, which needs to enable copy construction to enable the following:

at::Tensor b = at::rand(...);
// Oftentimes this will create a "view" of the tensor. a and b will point the the same underlying storage, but with different metadata.
at::Tensor a = b;

However, in the ExecuTorch delegate this is no longer necessary. Each Tensor is associated with it's own independent storage and is responsible for managing it's own memory. By getting rid of std::shared_ptr, we can avoid a heap allocation and avoid chasing pointers whenever we need to access the resources of a vTensor.

Differential Revision: D55811279

[pytorch-bot]

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[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D55811279

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D55811279

[facebook-github-bot]

This pull request has been merged in bf5093a.