[Feature Request]: Allow registering secondary sidebar extensions

### Is there an existing issue for this?

- [x] I have searched the existing issues and checked the recent builds/commits

### What would your feature do ?

Summary: The feature would be replicating all functionalities of the bottom panel, but would simpyl be positioned to the opposite side of the main sidebar (right by default).

Details: Allow adding sidebar extension tabs to a "secondary" sidebar. It would behave similar to the bottom panel in the sense that the sidebar would be hidden by default, but could have its visibility toggled. The location of the sidebar would be to the right by default, but could also be on the left -- it would depend on the location of the main sidebar.

### Proposed workflow

1. Register a secondary sidebar tab via the extension system
2. Enable opening via a hotkey or button
3. User presses the hotkey or button
4. The extension's component renders

### Additional information

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-3635-Feature-Request-Allow-registering-secondary-sidebar-extensions-1e06d73d365081d0a786f50d80c5d7e0) by [Unito](https://www.unito.io)