Java: Add Agents API consistent with .NET Agents/Abstractions (Beta release)

Implement the Semantic Kernel for Java Agents API, following the reference implementation in .NET.

The following work needs to be complete to get to a "Beta" status:

Microsoft.SemanticKernel.Agents.Core

Add this package to bring the core functionality online.

• This will get us the "hero path" which is to provide a code sample to create an Agent that uses the ChatCompletion functionality already in the SK.
  • Prioritize classes marked as "Experimental" as last to be done.
• Add further agent support in the Core functionality experience.
  • Azure AI (Foundry) agents
    • Foundry for Java not ready yet, but it's planned
    • NOTE: Foundry agent in .NET is still called the Azure AI agent.
  • other agents
  • Bedrock (should be done absolutely last, very difficult to work with.)

Microsoft.SemanticKernel.API

Add the agents abstractions to this package.

Microsoft.SemanticKernel.x

• Small fixups throughout that will support Agents and that will bring us into further parity with the reference (.NET) implementation.