Previously, the LibWeb bindings generator would output multiple per
interface files like Prototype/Constructor/Namespace/GlobalMixin
depending on the contents of that IDL file.
This complicates the build system as it means that it does not know
what files will be generated without knowledge of the contents of that
IDL file.
Instead, for each IDL file only generate a single Bindings/<IDLFile>.h
and Bindings/<IDLFile>.cpp.
As FontFaces are added or removed from a FontFaceSet, and as they load
or fail, the FontFaceSet moves them between a few different lists, and
updates its loading/loaded status. In the spec, this is how the
FontFaceSet.[[ReadyPromise]] gets fulfilled: When the document has
finished loading and FontFaceSet.[[LoadingFonts]] is empty, it resolves
the promise.
To support this, FontFace now keeps a set of FontFaceSets that it is
contained in.
This lets us remove the non-spec resolve_ready_promise() call in
EventLoop which was sometimes triggering before any fonts had attempted
to load.
As noted, there's a spec issue with the ready promise: If nothing
modifies the document's fonts, then it would never resolve. My ad-hoc
fix is to also switch the FontFaceSet to the loaded state if it is
empty, which appears to solve the issues but is not ideal.
The current css-font-loading spec doesn't define a constructor for this,
and from our own code we can rely on initializing things in the C++
constructor.
For simplicity, this requires that the setlike Foo class has a
`void on_set_modified_from_js(Badge<Bindings::FooPrototype>)` method.
This will be called after the set is modified from a generated `add()`,
`delete()`, or `clear()` method.
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
