Better documentation for self hosting agents

[jhammarstedt]

We host our services in our own kubernetes cluster and I think there's very lite documentation on how to build for that. There are a small chapter on deploying a custom streaming app and you can use the fastapi (get_fast_api_app) wrapper to get it done, but I still think there needs to be a much clearer documentation and support for not hosting in vertex while still being able to use the tools. The deployment docs even list self hosting as an option but then don't mention in in the list of available options https://google.github.io/adk-docs/deploy/

[hangfei]

Yes. We are working on a more general solution here: #184 . Documentation will be added along this work. Thanks.