.Net: AgentKernelPluginFactory.CreateFromAgents - enable direct support for agents implicitly

[joslat]

Motivation and Context

1. Why
   • it helps reduce cognitive overload and reduces the code to write, like in python
   • solves .NET Agents New Feature: When Adding an agent as a plugin it is too verbose, I want to do it like in Python! #11439
2. Need to write too much code to set an agent as a plugin:

var agentPlugin = KernelPluginFactory.CreateFromFunctions("AgentPlugin",
            [
                AgentKernelFunctionFactory.CreateFromAgent(this.CreateSalesAssistant()),
                AgentKernelFunctionFactory.CreateFromAgent(this.CreateRefundAgent())
            ]);

while in Python:
plugins=[billing_agent, refund_agent],

3. Scenario
   Making easier and simpler to write agentic code :)

4. Issue: .NET Agents New Feature: When Adding an agent as a plugin it is too verbose, I want to do it like in Python! #11439

Description

Added the change as an extension method as KernelPluginFactory is in SemanticKernel.Core without any reference to Agents.Core where the method is. Unsure you would like to add a reference to it in the SemanticKernel.Core, but it would be a lot more simpler to implement.

Now, the changes have been applied here:

semantic-kernel/dotnet/samples/GettingStartedWithAgents/Step08_AgentAsKernelFunction.cs

Line 71 in 0ff97c7

var agentPlugin = KernelPluginFactory.CreateFromFunctions("AgentPlugin",

So it would look instead of the above code as:

        KernelPlugin agentPlugin = KernelPluginFactoryExtensions.CreateFromFunctions("AgentPlugin",
            [
                this.CreateSalesAssistant(),
                this.CreateRefundAgent()
            ]);

Which is a little less verbose, and more similar to the Python code.

Contribution Checklist

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

[joslat]

@markwallace-microsoft all changes applied 👍

[SergeyMenshykh]

LGTM: having a unit test or a few would be helpful here.