gpui: Improve path rendering & global multisample anti-aliasing (#29718)

Currently, the rendering path required creating a texture for each path,
which wasted a large amount of video memory. In our application, simply
drawing some charts resulted in video memory usage as high as 5G.

I removed the step of creating path textures and directly drew the paths
on the rendering target, adding post-processing global multi-sampling
anti-aliasing. Drawing paths no longer requires allocating any
additional video memory and also improves the performance of path
rendering.

Release Notes:

- N/A

---------

Co-authored-by: Jason Lee <huacnlee@gmail.com>

crates/gpui/src/path_builder.rs

@@ -336,10 +336,7 @@ impl PathBuilder {
             let v1 = buf.vertices[i1];
             let v2 = buf.vertices[i2];
 
-            path.push_triangle(
-                (v0.into(), v1.into(), v2.into()),
-                (point(0., 1.), point(0., 1.), point(0., 1.)),
-            );
+            path.push_triangle((v0.into(), v1.into(), v2.into()));
         }
 
         path