.NET: Add integration tests for covering Tools and Sample scenarios for providers.

[rogerbarreto]

Motivation and Context

• Resolves .NET: Add integration tests covering all sample scenarios #713

[Copilot]

Pull request overview

This PR adds comprehensive integration tests for Tools and Sample scenarios across multiple AI providers, specifically focusing on image content handling and hosted tools functionality.

Key Changes

• Adds new RunWithImageContentWorksAsync test to conformance test base classes for validating vision/image analysis capabilities
• Implements hosted tools integration tests (Code Interpreter, File Search, Web Search, MCP) for AzureAI and AzureAIAgentsPersistent providers
• Adds shared test asset (walkway.jpg) with proper MSBuild configuration for distribution to test projects

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
dotnet/tests/AgentConformance.IntegrationTests/ChatClientAgentRunTests.cs	Added base conformance test for image content handling (non-streaming)
dotnet/tests/AgentConformance.IntegrationTests/ChatClientAgentRunStreamingTests.cs	Added base conformance test for image content handling (streaming)
dotnet/tests/OpenAIChatCompletion.IntegrationTests/OpenAIChatCompletionChatClientAgentRunTests.cs	Skips image content test for reasoning models which don't support images
dotnet/tests/OpenAIChatCompletion.IntegrationTests/OpenAIChatCompletionChatClientAgentRunStreamingTests.cs	Skips image content test for reasoning models (streaming version)
dotnet/tests/AzureAIAgentsPersistent.IntegrationTests/AzureAIAgentsPersistentRunTests.cs	Implements provider-specific image content test
dotnet/tests/AzureAIAgentsPersistent.IntegrationTests/AzureAIAgentsPersistentHostedToolsTests.cs	New file with comprehensive hosted tools tests (Code Interpreter, File Search, MCP, Web Search)
dotnet/tests/AzureAIAgentsPersistent.IntegrationTests/AzureAIAgentsPersistentFixture.cs	Adds helper methods for creating agents with tool definitions and web search tool configuration
dotnet/tests/AzureAI.IntegrationTests/AIProjectClientFixture.cs	Adds GetWebSearchTool helper method for test configuration
dotnet/tests/AzureAI.IntegrationTests/AIProjectClientChatClientAgentRunTests.cs	Overrides image content test with server error handling for known 500 errors
dotnet/tests/AzureAI.IntegrationTests/AIProjectClientChatClientAgentRunStreamingTests.cs	Overrides image content test with server error handling (streaming version)
dotnet/tests/AzureAI.IntegrationTests/AIProjectClientAgentHostedToolsTests.cs	New file with comprehensive hosted tools tests mirroring AzureAIAgentsPersistent structure
dotnet/tests/AnthropicChatCompletion.IntegrationTests/AnthropicChatCompletionChatClientAgentRunTests.cs	Skips image content test for Anthropic provider
dotnet/tests/AnthropicChatCompletion.IntegrationTests/AnthropicChatCompletionChatClientAgentRunStreamingTests.cs	Skips image content test for Anthropic provider (streaming version)
dotnet/src/Shared/IntegrationTests/Assets/walkway.jpg	Binary image asset for vision/image analysis testing
dotnet/eng/MSBuild/Shared.props	Configures shared assets to be copied to test output directories
dotnet/samples/AGUIClientServer/AGUIDojoServer/ChatClientAgentFactory.cs	Removes unused OpenAI using statement