canvas: Remove as much usage of font-kit as possible (#32758)

Do font selection using Servo's font backend, which is shared with the
rest of layout. In addition, delay the creation of the `font-kit` font
until just before rendering with `raqote`. The idea is that when
`raqote` is no longer used, we can drop the `font-kit` dependency.

This change has the side-effect of fixing text rendering in canvas,
adding support for font fallback in canvas, and also correcting a bug in
font selection with size overrides.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>

Cargo.lock

@@ -626,6 +626,7 @@ dependencies = [
 name = "canvas"
 version = "0.0.1"
 dependencies = [
+ "app_units",
  "bitflags 2.6.0",
  "byteorder",
  "canvas_traits",
@@ -641,8 +642,10 @@ dependencies = [
  "lyon_geom",
  "net_traits",
  "num-traits",
+ "parking_lot",
  "pathfinder_geometry",
  "pixels",
+ "range",
  "raqote",
  "servo_arc",
  "sparkle",
@@ -650,6 +653,7 @@ dependencies = [
  "style_traits",
  "surfman",
  "time 0.1.45",
+ "unicode-script",
  "webrender",
  "webrender_api",
  "webrender_traits",