Add docs for synced_collections

[vyasr]

Description

This PR adds synced_collections to all the relevant places in the docs and updates existing documentation where appropriate.

Motivation and Context

With the recent release of synced_collections it should be documented alongside the rest of the framework.

Checklist:

• [x] I am familiar with the Contributing Guidelines.
• [x] I agree with the terms of the Contributor Agreement.
• [x] My code follows the code style guideline of this project.

[vyasr]

Thanks Bradley!