Python: Improve agent getting started samples

[TaoChenOSU]

Motivation and Context

We are improving developer experience by updating the agent getting started samples.

Description

Simplify the agent getting started samples by removing unnecessary code and add excessive comments to make sure we are only doing what we need to get started.

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/azure_ai
agent_thread_actions.py	341	129	62%	140, 142, 177–180, 365, 367, 406–407, 433, 436–440, 443–455, 458–489, 495–502, 505–518, 534–565, 609, 612, 641–675, 738, 743–748, 768–775, 806–815, 858–868
azure_ai_agent.py	93	14	85%	95, 97, 103, 112–117, 119, 121, 142–145, 193, 253
semantic_kernel/agents/chat_completion
chat_completion_agent.py	110	7	94%	82, 85, 94–99, 124, 192
TOTAL	18839	2366	87%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3164	5 💤	0 ❌	0 🔥	1m 24s ⏱️