file_finder: Display file icons (#18091)

This PR adds file icons (like in tabs, the project panel and tab
switcher) to the file finder popup.

It's similar to [tab_switcher
icons](https://github.com/zed-industries/zed/pull/17115), but simpler,
because we're only dealing with actual files.

Release Notes:

- Added icons to the file finder.

Screenshot:

![image](https://github.com/user-attachments/assets/bd6a54c1-cdbd-415a-9a82-0cc7a0bb6ca2)

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Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>