Disambiguate the winml OrtModel with the model editing API OrtModel. (#24474)
### Description
<!-- Describe your changes. -->
Use a pimpl-esque approach so that the winml OrtModel type doesn't
conflict with the model editing API OrtModel.
### Motivation and Context
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- If it fixes an open issue, please link to the issue here. -->
Fix crash due to linker calling the incorrect destructor when there are
two different OrtModel types in the global namespace.