In commit 1b82cb43c2 I accidentally
removed the paint transformation altogether. The result was that
zoomed-in SVGs, or SVG elements with a transformation applied could have
their gradient coordinates misplaced significantly.
This was also exposed in the `svg-text-effects` test by way of a slight
visual difference. Add a new test that very clearly exposes the fixed
issue by rotating the gradient coordinates by 45 degrees.
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
We currently have 2 virtual methods to inform DOM::Element subclasses
when an attribute has changed, one of which is spec-compliant. This
patch removes the non-compliant variant.
