[CXX] Introduce C++ API for new C entry points

[yuslepukhin]

Description

Create or augment existing C++ API for new entry points

Motivation and Context

Enable exception safe coding in C++ codebase.

[Copilot]

Pull Request Overview

Introduces C++ API wrappers for new C entry points to enable exception-safe coding in C++ codebase by replacing raw C API calls with C++ wrappers that provide RAII and exception handling.

• Creates C++ wrapper classes for graph, node, value info, and operator attribute APIs
• Implements exception-safe methods that wrap existing C API calls
• Migrates test code from raw C API usage to new C++ wrappers

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
onnxruntime/test/shared_lib/test_model_builder_api.cc	Updates method calls from Name() to GetName() for graph inputs
onnxruntime/test/ep_graph/test_ep_graph_topo_sort.cc	Replaces C API calls with C++ wrappers and adds exception handling
onnxruntime/test/ep_graph/test_ep_graph.cc	Migrates from raw C API to C++ wrapper APIs for graph traversal and attribute access
onnxruntime/test/autoep/library/example_plugin_ep_utils.h	Updates function signature to use C++ wrapper types
onnxruntime/test/autoep/library/example_plugin_ep_utils.cc	Implements exception-safe versions using C++ wrappers
onnxruntime/test/autoep/library/example_plugin_ep.cc	Adds C++ API initialization and migrates kernel implementation
onnxruntime/test/autoep/library/ep.h	Fixes duplicate class qualifier
onnxruntime/test/autoep/library/ep.cc	Comprehensive migration to C++ API with exception handling
include/onnxruntime/core/session/onnxruntime_cxx_inline.h	Implements inline methods for new C++ wrapper classes
include/onnxruntime/core/session/onnxruntime_cxx_api.h	Defines new C++ wrapper classes and type aliases
include/onnxruntime/core/providers/utils/ort_graph_to_proto.h	Migrates utility functions to use C++ wrappers

Comments suppressed due to low confidence (2)

onnxruntime/test/ep_graph/test_ep_graph.cc:1

• Logic error: The condition should be op_type == "Mul" instead of op_type != "Mul". The current condition will process non-Mul nodes and skip Mul nodes, which is opposite to the intended behavior based on the subsequent code that expects Mul operations.

// Copyright (c) Microsoft Corporation. All rights reserved.

onnxruntime/test/autoep/library/ep.cc:1

• Comment parameter name is misspelled. Should be 'value_info' instead of '/* value_info */'.

// Copyright (c) Microsoft Corporation. All rights reserved.

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