We already had the API, but drawing to the canvas was not affected by
any created CanvasPattern. This moves CanvasPatternPaintStyle to LibGfx
so we don't have to reach into LibWeb, and implements the plumbing to
let Skia use images as a fill pattern.
This isn't a full fix, as the paint function does not handle this
either. But instead of getting the bitmap from the image source
immediately, follow the spec a bit more closely by creating the
CanvasPatern object with the ImageSource directly.
Fixes a crash for the 5 included WPT tests.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
