.NET Agent - Add AIContext to OpenAIResponseAgent

[crickman]

Motivation and Context

Follow-up to #12444

Fixes: #12472

Description

Add support for incorporating AIContext when invoking OpenAIResponseAgent
Enabled conformance tests

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Unrelated integration test failure

[xUnit.net 00:06:04.80]     SemanticKernel.IntegrationTests.Connectors.AzureOpenAI.AzureOpenAIChatClientRequiredFunctionChoiceBehaviorTests.SpecifiedInPromptInstructsConnectorToInvokeKernelFunctionAutomaticallyAsync [FAIL]
[xUnit.net 00:06:04.80]       Polly.Timeout.TimeoutRejectedException : The operation didn't complete within the allowed timeout of '00:00:30'.
[xUnit.net 00:06:04.80]       ---- System.Threading.Tasks.TaskCanceledException : The operation was canceled.
[xUnit.net 00:06:04.80]       -------- System.IO.IOException : Unable to read data from the transport connection: Operation canceled.
[xUnit.net 00:06:04.80]       ------------ System.Net.Sockets.SocketException : Operation canceled