gpui: Add more shapes for `PathBuilder` (#30904)

- Add `arc` for drawing elliptical arc.
- Add `polygon` support.

<img width="1136" alt="image"
src="https://github.com/user-attachments/assets/97032b02-e6ff-4985-a587-3689500bfd56"
/>

Release Notes:

- N/A
c73af0a52fFloyd Wang committed on 5/26/2025, 9:49:42 AM· committed by GitHubparente42cf21
2 files changedLine totals unavailable