Support for AgentThreadStore / CacheStore

[Shubham-Kumar-2000]

So I was working on the integration of A2A protocol [PR] where when the same contextId is passed from the client end then the agent should have the context of all the past ChatMessages on the same id.

Now as agents in agent_framework are stateless and context is managed through AgentThreads we need to have a mapping between contextId and threads such that we can reuse threads when we get the same id.

To enable this as a library I wanted to have a Store interface that the users may override to store threads in their preferred location.
But didn't find any such out of box support in core library.

I remember there was something called CacheStore in autogen that was a generalised store for any entity.

Should can we add support for a generalised store or a specific AgentThreadStore for only storing AgentThreads ?

Or is there a better way to achieve this that I am missing.

[eavanvalkenburg]

@Shubham-Kumar-2000 we are considering doing a update to the way threads are created and used, which includes a clearer story around this topic: #2420