Python: Update Agent invoke abstraction parameters

[TaoChenOSU]

Motivation and Context

Now that our agents have a more aligned interface, we can move the common interface parameters to the abstract class.

Description

Move the messages and thread parameters to the abstract class Agent for the get_response, invoke, and invoke_stream methods.

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
agent.py	150	22	85%	46, 53, 57, 66–77, 124, 129, 134, 139, 144, 148, 152, 156, 305–307, 374
semantic_kernel/agents/autogen
autogen_conversable_agent.py	117	15	87%	68, 74, 86, 88, 93–97, 278–279, 288–291
semantic_kernel/agents/bedrock
bedrock_agent.py	250	54	78%	77–84, 93, 159, 286, 299, 318, 334–337, 343, 345, 348, 353, 383, 396, 428–448, 452, 482, 495, 514–517, 519–522, 564, 575–576, 588, 624–635, 646, 663–676, 693–702
bedrock_agent_base.py	145	43	70%	103, 121–122, 147, 160–162, 189, 208–210, 215, 234–236, 241, 245–246, 266–268, 277, 296–300, 305, 324–328, 333, 345–347, 359–381
semantic_kernel/agents/channels
bedrock_agent_channel.py	79	2	97%	208–209
TOTAL	21224	2461	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3335	5 💤	0 ❌	0 🔥	1m 40s ⏱️