Fixed webnn test crash issue (#34708) (#34831)
### Details:
- In the debugger, I found the `read_to` located at `openvino.dll`. All
other plugin call the `read_to` method to construct a string will
allocate the memory in `openvino.dll`
- The `onnxruntime_providers_openvino_plugin_impl.dll`'s new feature
will convert `float` map to `std::string`. The `float` map `Any` object
was created at `openvino_intel_npu_plugin.dll`. So the `_impl` in `Any`
is `openvino_intel_npu_plugin`'s type. `_temp` is
`onnxruntime_providers_openvino_plugin_impl`'s `string` type. Then the
`Any`'s dtor will call the
`onnxruntime_providers_openvino_plugin_impl`'s `string` dtor. That
caused the memory issue.
### Solution:
- Create a virtual method `read_from` and let the copy call the real
type's method. In this way, it can call the
`onnxruntime_providers_openvino_plugin_impl`'s ctor and dtor.
- Port https://github.com/openvinotoolkit/openvino/pull/34708
### Tickets:
- [CVS-182610](https://jira.devtools.intel.com/browse/CVS-182610)
### AI Assistance:
- *AI assistance used: no / yes*
- *If yes, summarize how AI was used and what human validation was
performed (build/tests/manual checks).*
Co-authored-by: Pawel Raasz <pawel.raasz@intel.com>
