Python: Add framework name into UserAgent header for bedrock integration

[0x-fang]

Motivation and Context

This PR adds the framework name into User-Agent header of Bedrock API call, so it can be used to collect the usage.

Description

Updated integration with Amazon Bedrock services to include the framework name semantic-kernel into the User-Agent header field for Bedrock API call for improved client identification. No changes to user-facing features or workflows. Similar change had been made to other framework such as langchain

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 😄

[0x-fang]

Hi @moonbox3 @dmytrostruk @eavanvalkenburg Could you please kindly help take a look and merge this small change if possible? Thank you very much!

[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
connectors/ai/bedrock/services
bedrock_base.py	14	0	100%
TOTAL	27113	4727	82%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3715	22 💤	0 ❌	0 🔥	1m 42s ⏱️