gpui: Add `truncate` and `text_ellipsis` to TextStyle (#14850)

Release Notes:

- N/A

Ref issue #4996

## Demo

```
cargo run -p gpui --example text_wrapper 
```



https://github.com/user-attachments/assets/a7fcebf7-f287-4517-960d-76b12722a2d7

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