Allow zero-element tensors to get set

[RyanMetcalfeInt8]

Description

This PR fixes an issue where zero-element tensors (typically when ort_ptr is nullptr) are not properly converted to OpenVINO tensors and set on the infer request.

Motivation and Context

For ORT GenAI use cases, it's possible that the application will pass zero-element tensors as input for inference. For example, for whisper pipeline through ORT GenAI, the first decode inference will set a 'past' KVCache tensor of shape [1, 8, 0, 64]. As this has 0 total elements, typically the ort_ptr associated with it is also nullptr.

Previously, this condition (if (cached_binding.ort_ptr != ort_ptr) {) needed to be true in order to create an ov::Tensor and set it on the infer request. But, for a zero-element tensor, both of these are NULL and so the tensor does not get set -- which causes various issues.

This PR adds an else that specifically checks for this 'zero-element' tensor case.

With this PR, I am able to run onnxruntime-genai whisper pipelines with OVEP.

Note: I didn't want to overcomplicate this PR, but I do think that this function should get revisited / refactored a bit. Comparing only the ptr is quite dangerous. For example, it's possible that the application can create a different shaped Ort tensor from the same buffer location -- so I think we should at least compared the ptr and the shape...

[ankitm3k]

lgtm, merging this change for now. We will revisit this change given it doesn't impact the other non genai models