Python: split kernel into kernel extensions for relevant pieces

[eavanvalkenburg]

Motivation and Context

In order to keep better track of related pieces within the Kernel, including easier unit testing, this PR splits the kernel into pieces that are self-contained, but abstract.

Description

New:

• KernelServicesExtension
• KernelFunctionExtension
• KernelReliabilityExtension

Changed:

• Kernel, now imports the new ones.
• KernelFiltersExtension, moved to filters folder, in line with the rest.

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 3.10 Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel
kernel.py	95	39	59%	127, 134–143, 173, 183–191, 263–299
semantic_kernel/connectors/ai/open_ai/services
open_ai_chat_completion_base.py	212	93	56%	98, 118, 143–147, 171, 175, 191–196, 213–241, 244–255, 273–280, 291–299, 315–322, 343, 351, 357–363, 375–381, 412, 451, 453–454, 459–464, 468–475, 497, 506–515
semantic_kernel/functions
kernel_function.py	82	2	98%	145, 165
kernel_function_extension.py	126	11	91%	45, 47, 115–116, 343, 364–366, 402, 404, 414
kernel_function_from_prompt.py	157	7	96%	149–150, 171, 191, 216, 237, 317
TOTAL	6260	1031	84%

Python 3.10 Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1341	1 💤	0 ❌	0 🔥	13.215s ⏱️

[Josephrp]

awesome pythonic refactor 👏🏻👏🏻