Interface may block when restoring folder on external drive, FTP or DAV

## Problem

I often findmyself staring at the Files window waiting for it to unfreeze because I committed the heinous act of forgetting to close a tab that was opened in a folder on my external hard drive. The same is even worse for FTP and DAV(S), as it can last indefinitely while realistically you probably didn't even open the app to view that folder.

## Proposal

The same with AppCenter loading its update; make the folder and tab loading process separate from the UI so that these issues do not arise - maybe even add a timeout if the directory is really dragging the entire app down.

## Prior Art

Pretty sure this is what macOS has done for a long time, it's certainly what iOS Documents does