changes to AgentBase and HostBuilderExtensions to enable leveraging handlers from composition (interfaces) vs inheritance... see HelloAgents sample for usage
closes#3928
is related to #3925
adopts the new Microsoft.Extensions.AI abstractions
adds a base InferenceAgent
fixes a lot of pain points in the runtime wrt startup/shutdown
fixes some uncaught exceptions in the grpc stream reading
adds an example for running the backend service in its own process
adds an example of an agent that connects to OpenAI/Ollama
adds an example of wrapping an agent app in .NET Aspire
upgrades some dependencies and removes some others
Known bugs: #3922
