feat: add support for unique reactions

[isekovanic]

🎫 Ticket: https://linear.app/stream/issue/REACT-581/add-support-for-enforcing-unique-reactions

📑 Docs: https://github.com/GetStream/docs-content/pull/

💡 Overview

This PR adds support for unique reactions within the SDK.

Unique reactions always trigger the comment.reaction.updated or activity.reaction.updated events so we can use them as some fine-grained control to determine which reaction action is happening. We mainly need this in order to modify own_reactions adequately on the parent entity, as it won't arrive through WS events.

Since this is a preliminary PR before this is deployed on our BE, we have to wait for this PR to be deployed before merging this one.

The PR's been tested against WS events, HTTP response state updates (and of course both).

TODO:

• Tests
• Docs
• (optional, probably better to do it later) Clean up the reaction actions to eliminate code duplication

📝 Implementation notes