Python: Agent get_response API

[TaoChenOSU]

Motivation and Context

With the recent push for improving developer's quality of life, we have decided to make it easier for developers to get started with agents by introducing a new get_response API, that hides the complexity of interacting with agents when developers are ramping up with the Agent concept.

Description

1. Add the get_response API on all agent types. This API skips hides the intermediate steps of the agent execution and only returns the final results as a single message.
2. Add tests and samples.
3. Updates the Agent class to be an ABC, and adds get_response, invoke, and invoke_stream methods as overridable.

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
semantic_kernel/agents/autogen
autogen_conversable_agent.py	72	7	90%	85, 181–182, 191–194
semantic_kernel/agents/azure_ai
agent_content_generation.py	148	20	86%	68–71, 89, 91, 303, 355–387
agent_thread_actions.py	341	129	62%	142, 144, 179–182, 369, 371, 410–411, 437, 440–444, 447–459, 462–493, 499–506, 509–522, 538–569, 613, 616, 645–679, 742, 747–752, 772–779, 810–819, 862–874
azure_ai_agent.py	115	15	87%	105, 107, 113, 122–127, 129, 131, 152–155, 204, 269, 330
semantic_kernel/agents/bedrock
bedrock_agent.py	216	41	81%	115, 129, 133, 135, 182–195, 261, 285, 302, 335, 354, 370–373, 379, 381, 384, 388, 420, 450–459, 470, 502, 519–520, 522–523, 565, 576–577, 589, 625–636, 647, 664–677
semantic_kernel/agents/chat_completion
chat_completion_agent.py	125	8	94%	92, 95, 104–109, 187, 251, 311
semantic_kernel/agents/open_ai
assistant_thread_actions.py	317	38	88%	107, 110, 113, 190, 192, 229–235, 405, 463, 480, 567–576, 612–626, 638–639, 710, 715, 747
open_ai_assistant_agent.py	196	6	97%	231, 244, 280, 450, 541, 629
TOTAL	18993	2378	87%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3197	5 💤	0 ❌	0 🔥	1m 31s ⏱️