[Feature Request] Add mechanism for helping identify what driver version was used in compiling a model

### Describe the feature request

There is metadata in EPContext operator schema which identifies the SDK version that a model was compiled with. This feature request tracks adding a new string element for an `ep_driver_version` attribute which helps identify the associated driver version.

### Describe scenario use case

A caller may want to interrogate a model to understand what EP _and driver_ version it was compiled with (e.g., as part of a compatibility check for example). The driver version may be relevant given that different versions of a driver might not preserve compatibility with a given EP.

Start by locating the EPContext operator schema and the existing metadata element that records the SDK version. Trace how callers interrogate that metadata and determine where the new ep_driver_version string belongs. Done means a compiled model exposes the associated driver version alongside the EP and SDK information, with coverage for reading the new attribute.

Written by the indexing model from the issue text.