gpui: Add PathBuilder based on lyon to build Path (#22808)

Release Notes:

- N/A

---

Continue https://github.com/zed-industries/zed/pull/20499

We to draw more complex Path. Before this change, we only have
`line_to`, but it is not enough.

Add a new `PathBuilder` to use [lyon](https://github.com/nical/lyon) to
build more complex path.

And then with PR #22812 to enable anti-aliasing, all thing will be
perfect.
## Show case

```bash
cargo run -p gpui --example painting
```

Before:

<img width="1136" alt="image"
src="https://github.com/user-attachments/assets/0c15833a-ec95-404c-a469-24cf172cfd86"
/>

After:

<img width="1136" alt="image"
src="https://github.com/user-attachments/assets/42cfa35e-7e8f-4ef3-bb2d-b98defc62ad6"
/>

crates/gpui/src/scene.rs

@@ -715,6 +715,13 @@ impl Path<Pixels> {
         }
     }
 
+    /// Move the start, current point to the given point.
+    pub fn move_to(&mut self, to: Point<Pixels>) {
+        self.contour_count += 1;
+        self.start = to;
+        self.current = to;
+    }
+
     /// Draw a straight line from the current point to the given point.
     pub fn line_to(&mut self, to: Point<Pixels>) {
         self.contour_count += 1;
@@ -744,7 +751,8 @@ impl Path<Pixels> {
         self.current = to;
     }
 
-    fn push_triangle(
+    /// Push a triangle to the Path.
+    pub fn push_triangle(
         &mut self,
         xy: (Point<Pixels>, Point<Pixels>, Point<Pixels>),
         st: (Point<f32>, Point<f32>, Point<f32>),