Display file icons in tabs (#14523)

This PR adds support for displaying file icons in tabs.

The `tabs.file_icons` setting controls whether the icons are displayed:

```json
{
  "tabs": {
    "file_icons": false
  }
}
```

This setting defaults to `true`.

<img width="1566" alt="Screenshot 2024-07-15 at 6 17 26 PM"
src="https://github.com/user-attachments/assets/86dfc8c9-764c-453d-95e4-2ec95d6fe715">

<img width="1566" alt="Screenshot 2024-07-15 at 6 24 26 PM"
src="https://github.com/user-attachments/assets/4b4e8489-49d3-41bf-b4cb-59365bdd3e9d">

Release Notes:

- Added file icons to buffer tabs
([#12138](https://github.com/zed-industries/zed/issues/12138)).
- If desired, these icons can be removed using `"tabs": { "file_icons":
false }`.