OVEP: Tensor caching fix (#22218)
### 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).
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Co-authored-by: Eric Crawford <eric.r.crawford@intel.com>
