Feat]: Client-side utility for assembling artifacts from update events #1030

Is your feature request related to a problem? Please describe.

1.0 release removed ClientTaskManager (see #734) and changed client API in a way that it now closely mirrors server API and uses StreamResposne as a return type.

#734 mentions a possible helper for reconstructing artifacts specifically, this issue is to track it.

Describe the solution you'd like

As stated in #734 maintaining the whole Task state locally can result in divergence with server state and should not be relied on by default (especially due to history behavior specification in 1.0, #734 has more details).

For artifacts though the logic is deterministic and can be replicated locally if one wants to maintain full artifact state by interpreting append and lastChunk flags. Client API should not be changed here, new helper should operate on a stream of StreamResponse.