Previously most of the calculations for `object-fit` and
`object-position` were based on device pixels, meaning that images would
render differently based on zoom and DPI settings. Instead those
calculations now use css pixels and only the final draw-call is based
on device-pixels.
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
Now that the heap has no knowledge about a JavaScript realm and is
purely for managing the memory of the heap, it does not make sense
to name this function to say that it is a non-realm variant.
