[Feat] Support Streaming Agent Results

[adamfweidman]

What would you like to be added?

Allow invocations of remote agents to stream back content

Why is this needed?

A2A Agents can stream text/tasks/artifacts back to the client. We should display these to the user as they are received.

Additional context

No response

[ishaanxgupta]

Hi @hminooei @adamfweidman,
I would love to work on this issue, just a small doubt whether #15091 should be solved first before proceeding on this one or this is a separate issue?