Python: streaming agent response callback in agent orchestrations

[TaoChenOSU]

Motivation and Context

Issue: #12306
Discussion: #12302

Currently, we only have a non-streaming agent response callback for users to interact with the agents inside an orchestration. Support for a stream one has been requested by developers.

Description

Add support for a streaming agent response callback to all orchestrations.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
agents/orchestration
agent_actor_base.py	61	6	90%	33, 79, 96, 127, 147, 150
concurrent.py	72	0	100%
group_chat.py	191	13	93%	111, 114–117, 119–120, 122, 314–316, 318, 383
handoffs.py	193	26	86%	224–225, 229–231, 254, 257–260, 262, 264, 271, 279, 293, 297–298, 301, 312–313, 318, 330–333, 364
magentic.py	294	104	64%	122–124, 256, 379, 447, 450, 457, 461, 463, 490–495, 497, 502, 504, 510, 512, 517–518, 520–521, 527, 529–530, 533–534, 540, 548–549, 558, 561–562, 564–567, 570–571, 575–578, 580–581, 583, 585–591, 594–595, 602, 611–613, 615, 617, 625–626, 628, 633, 637–638, 640, 642–643, 647–648, 650, 653, 658–660, 663, 665, 679–682, 688, 690–691, 697, 701–702, 704, 706, 710, 712, 714, 723–727, 794–795
orchestration_base.py	123	5	95%	65, 168, 173, 178, 201
sequential.py	64	0	100%
TOTAL	27108	4625	82%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3623	22 💤	0 ❌	0 🔥	1m 47s ⏱️