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/window.rs

@@ -2633,7 +2633,7 @@ impl Window {
         path.color = color.opacity(opacity);
         self.next_frame
             .scene
-            .insert_primitive(path.scale(scale_factor));
+            .insert_primitive(path.apply_scale(scale_factor));
     }
 
     /// Paint an underline into the scene for the next frame at the current z-index.