Add GetCapability/Compile infrastructure for EP ABI (#24887)
### Description
This PRs sets the foundation for the EP ABI, which allows plugin-EPs to
interface with ORT using a binary stable interface. A plugin-EP can be
built separately from ORT and is not tied to a specific commit of ORT.
Currently, this PR adds basic APIs necessary to allow an example
plugin-EP to compile and run a simple model with a single `Mul` node.
- Example plugin-EP implementation:
https://github.com/microsoft/onnxruntime/blob/adrianl/ep-abi/onnxruntime/test/autoep/library/example_plugin_ep.cc
- APIs:
- Graph IR:
https://github.com/microsoft/onnxruntime/blob/adrianl/ep-abi/include/onnxruntime/core/session/onnxruntime_c_api.h#L5290-L5439
- Plugin EP:
https://github.com/microsoft/onnxruntime/blob/adrianl/ep-abi/include/onnxruntime/core/session/onnxruntime_c_api.h#L6177-L6481
- Example app code (from unit tests):
https://github.com/microsoft/onnxruntime/blob/adrianl/ep-abi/onnxruntime/test/autoep/test_autoep_selection.cc#L614
### Motivation and Context
Based on https://github.com/microsoft/onnxruntime/pull/21450
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Edward Chen <18449977+edgchen1@users.noreply.github.com>