.Net: Allow Kernel to be mutable by AgentChatCompletions

[RogerBarreto]

Motivation and Context

• Fixes .Net: Bug: Kernel.Data no longer retains information across plugins since v1.54 #12534

• This regression seems to be part of .Net: Add AIContextProvider support to Semantic Kernel #11689 where kernel instance was is cloned prior agent iterations, as I didn't captured any failing unit tests for the added AIContext providers considering this as a valid fix.

• Added UT covering the expected Kernel mutability.

[markwallace-microsoft]

@RogerBarreto is this integration test failure related to your changes?

[xUnit.net 00:05:48.23]     SemanticKernel.IntegrationTests.Connectors.AzureOpenAI.AzureOpenAIChatClientRequiredFunctionChoiceBehaviorTests.SpecifiedInPromptInstructsConnectorToInvokeKernelFunctionAutomaticallyAsync [FAIL]
[xUnit.net 00:05:48.23]       Polly.Timeout.TimeoutRejectedException : The operation didn't complete within the allowed timeout of '00:00:30'.
[xUnit.net 00:05:48.23]       ---- System.Threading.Tasks.TaskCanceledException : The operation was canceled.
[xUnit.net 00:05:48.23]       -------- System.IO.IOException : Unable to read data from the transport connection: Operation canceled.
[xUnit.net 00:05:48.23]       ------------ System.Net.Sockets.SocketException : Operation canceled

[westey-m]

This change will result in a regression elsewhere, since it means that AIContextProviders will permanently mutate the kernel plugin list, and this mutation is expected to be per iteration only.
Let's discuss this further in the standup before committing.

[RogerBarreto]

Let's discuss this further in the standup before committing.

Agree, actually the AIContext feature introduced this regression. I'm happy suggesting an alternative path for impacted customers using Agents with "Kernel data based functions".

[RogerBarreto]

@markwallace-microsoft This is unrelated error, I tried to run against my local configuration in Azure IT tests and passed as expected.