eStorage Tensors are currently unusable as OpTensorCreate calls mapDataIntoHostMemory

[axsaucedo]

As reported by @alexander-g in #14:

It seems they are currently unusable. I cannot use OpTensorCreate with them because this op tries to call mapDataIntoHostMemory() on them which is only valid for staging tensors. I also cannot manually call init() because I cannot access the Manager's vk::PhysicalDevice and vk::Device which are private.

Following up the response was:

Storage tensors may still be useful if the users want to make available memory to use within the GPU that would only be used to store data as any processing is being computed but it's not expected to be used to be sent back to the host. I will open an issue to make sure this is addressed.

This issue encompassess the exploration to first fix the way to make the tensors functional. This could go as part of #48 which coudl involve having a OpTensorInitialise function that only initialises / reinitialises a tensor, which currently is not possible in a simple way.

[axsaucedo]

This was resolved via #138