.NET: Update to latest Azure.AI.*, OpenAI, and M.E.AI*

[stephentoub]

Absorb breaking changes in Responses surface area PR.

• Fixes .NET: MissingMethodException on AIProjectClient.GetAIAgent #2869

[Copilot]

Pull request overview

This PR updates dependencies to the latest versions of Azure.AI., OpenAI, and Microsoft.Extensions.AI. packages and absorbs breaking changes from the OpenAI Response API surface area. The primary changes involve renaming types and methods to align with the updated SDK naming conventions.

• Renamed OpenAIResponseClient → ResponsesClient
• Renamed OpenAIResponse → ResponseResult
• Renamed ResponseCreationOptions → CreateResponseOptions
• Renamed GetOpenAIResponseClient() → GetResponsesClient()
• Updated namespaces from OpenAIResponse.IntegrationTests to ResponseResult.IntegrationTests
• Removed Azure.AI.Inference package and related code
• Updated package versions for Azure.AI.Projects, Azure.AI.OpenAI, OpenAI, and Microsoft.Extensions.AI packages

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
dotnet/Directory.Packages.props	Updated package versions for Azure.AI., OpenAI, and M.E.AI. dependencies; removed Azure.AI.Inference
dotnet/.editorconfig	Added diagnostic suppression for CA2252 (preview features)
dotnet/tests/OpenAIResponse.IntegrationTests/*.cs	Updated namespace to ResponseResult.IntegrationTests and string constants
dotnet/tests/Microsoft.Agents.AI..UnitTests/.cs	Updated type and method names to match new SDK naming
dotnet/tests/AzureAI.IntegrationTests/AIProjectClientFixture.cs	Updated method call to AsResponseResultItem()
dotnet/src/Microsoft.Agents.AI.*.cs	Updated type names, method calls, and API usage throughout
dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/Responses/Models/ConversationReference.cs	Changed serialization to always use object format rather than conditional string/object
dotnet/samples//.cs	Updated client creation and type references across all samples
dotnet/samples/AgentWebChat/AgentWebChat.AgentHost/*.cs	Removed Azure.AI.Inference integration code
.github/upgrades/prompts/SemanticKernelToAgentFramework.md	Updated example code with new type names

[markwallace-microsoft]

Integration tests are failing. This integration test has issues and needs to be skipped.

[xUnit.net 00:00:12.33]     Microsoft.Agents.AI.Workflows.Declarative.IntegrationTests.MediaInputTest.ValidateFileUrlAsync(fileSource: "https://sample-files.com/downloads/images/jpg/web_"···, mediaType: "image/jpeg") [FAIL]
[xUnit.net 00:00:12.33]       Assert.NotEmpty() Failure: Collection was empty
[xUnit.net 00:00:12.33]       Stack Trace: