OVEP: fix tensor regression

[saurabhkale17]

Description

1. changing the emplace to [] that does have a difference, emplace will only create a new entry if it doesn't already exist in the map
2. change the logic of the caching lookup to key off of input/output names instead of ort raw ptrs.
3. changes OV tensor creation for CPU allocated input/output ORT tensors. The CPU allocated input/output tensor path was re-allocating OV tensors based on the ORT input/output tensors. So we'd get 2 copies: ORT input/output tensor -> OV tensor (OVEP) -> NPU Tensor (NPU plugin).

[sfatimar]

LGTM