Python: Enable mypy for connector utils and search connectors. Improve code quality.

[moonbox3]

Motivation and Context

We have mypy enabled on parts of the code base, but not all. The goal is to enable it across the entire SK python code. As part of this, we've broken up the work to tackle different sections. Additionally, we're working to improve the code coverage for these sections of code.

Description

This PR:

• turns on mypy for the connector utils and the search connectors (Bing and Google). Small Code adjustments were made per mypy.
• other refactoring to make the code cleaner like using https AsyncClient, and better error handling around the API call.
• introduces Google Search settings for the connector.
• adds more unit test coverage for the document loader util and the Bing/Google search connectors. There is 100% code coverage.
• closes Python: CQ Spike: Utils & Search Engine #7136

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/connectors/search_engine
bing_connector.py	44	33	25%	38, 47–99
google_connector.py	37	26	30%	22–29, 33–65
semantic_kernel/connectors/utils
document_loader.py	17	1	94%	27
TOTAL	6664	623	91%

Python 3.10 Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1644	1 💤	0 ❌	0 🔥	24.461s ⏱️