✨ Async File Loading

### Description

Currently, CodeEdit loads the file tree of a workspace synchronously. For large folders this becomes slow and CodeEdit just waits and does nothing, until all files have been loaded.

Asynchronous loading of the filetree allows CodeEdit to do other useful things while waiting on the files from disk.

In practice, this will shorten the perceived startup time of CodeEdit by the user.

### Alternatives Considered

_No response_

### Additional Context

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### Screenshots

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