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/build.rs

@@ -126,7 +126,7 @@ mod macos {
             "ContentMask".into(),
             "Uniforms".into(),
             "AtlasTile".into(),
-            "PathRasterizationInputIndex".into(),
+            "PathInputIndex".into(),
             "PathVertex_ScaledPixels".into(),
             "ShadowInputIndex".into(),
             "Shadow".into(),