Python: preprend 'Semantic-Kernel' to User-Agent, and add version key-value pair to headers

[moonbox3]

Motivation and Context

The SK Python custom headers to track the USER_AGENT and the Python version were getting stuck into the default headers under the USER_AGENT key. Instead, they need to be represented like:

    {
        "UserAgent": HTTP_USER_AGENT,
        "Semantic-Kernel-Version": f"python-{version_info}",
    }

Trying to extract the Python version from telemetry data was not working as expected.

Description

Use the APP_INFO dict as-is, and stick the key-value pairs into the default_headers.

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 3.8 Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/connectors/ai/open_ai/services
azure_config_base.py	34	2	94%	80, 96
open_ai_config_base.py	32	1	97%	56
TOTAL	5399	1012	81%

Python 3.8 Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1205	11 💤	0 ❌	0 🔥	21.930s ⏱️

[eavanvalkenburg]

LGTM

[juliomenendez]

LGTM