feat: Integrate Brave Web Search API in search toolkit (#1005)

[MuggleJinx]

Description

Brave Web Search API is a REST API to query Brave Search and get back search results from the web.
This PR enhance the search toolkit with the Brave Web Search API.

Motivation and Context

Closes issue #1005.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of example)

Implemented Tasks

• Add one new model type in Gemini model series.
• Edit the corresponding example, and test file.

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.

[liuxukun2000]

Hi @MuggleJinx! Thank you for your contribution! Could you please add a comment at the end of the example file to indicate the expected output for this example? You can refer to the other examples for guidance. Thanks!

[Wendong-Fan]

Thanks @MuggleJinx ! Overall LGTM, some minor change required