Modify params for bedrock retrieve generate

[warren830]

Summary

Resolves #13201

In addition, add return type for bedrock_retrieve

Screenshots

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]

Please link an existing issue or creating one.

[warren830]

Please link an existing issue or creating one.

Thanks for review, I should have set this as a draft yesterday