canvas: Use vello_cpu as default canvas backend (#38844)

We really want to remove font-kit from dep tree, so this is the first
step into removing raqote from servo. While vello_cpu is not perfect
replacement, I am confident that we will resolve all issues eventually:
https://github.com/servo/servo/issues/38345 (most important ones already
have PRs).

Reviewable per commit.

Testing: Existing WPT tests.
Try run: https://github.com/sagudev/servo/actions/runs/17138369290

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/canvas/canvas_paint_thread.rs

@@ -313,6 +313,12 @@ impl Canvas {
             .to_lowercase()
             .as_str()
         {
+            #[cfg(feature = "vello_cpu")]
+            "" | "auto" | "vello_cpu" => Some(Self::VelloCPU(CanvasData::new(
+                size,
+                compositor_api,
+                font_context,
+            ))),
             #[cfg(feature = "raqote")]
             "" | "auto" | "raqote" => Some(Self::Raqote(CanvasData::new(
                 size,
@@ -325,12 +331,6 @@ impl Canvas {
                 compositor_api,
                 font_context,
             ))),
-            #[cfg(feature = "vello_cpu")]
-            "" | "auto" | "vello_cpu" => Some(Self::VelloCPU(CanvasData::new(
-                size,
-                compositor_api,
-                font_context,
-            ))),
             s => {
                 warn!("Unknown 2D canvas backend: `{s}`");
                 None

components/servo/Cargo.toml

@@ -21,7 +21,7 @@ bluetooth = [
     "script/bluetooth",
     "script_traits/bluetooth",
 ]
-default = ["clipboard", "raqote"]
+default = ["clipboard", "vello_cpu"]
 clipboard = ["dep:arboard"]
 crown = ["script/crown"]
 debugmozjs = ["script/debugmozjs"]