Feat(tools) add tavily extract tool and enhance tavily search implementation

[fdb02983rhy]

Summary

• Add new Tavily Extract tool for web content extraction
• Update Tavily Search tool parameter handling and validation
• Always return both text and json
• Return LLM-friendly Markdown formatted text

Fix #10785

Screenshots

Tavily Extract

REC-20241118003559.mp4

Tavily Search

REC-20241118004438.mp4

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[crazywoola]

Thanks ：）LGTM