Corresponds to https://github.com/whatwg/html/pull/10683
As part of this, I noticed we incorrectly were setting the "is popup"
flag on the Navigable instead of the BrowsingContext. I've fixed that
and removed the erroneous flag from Navigable.
These interfaces are exposed on *, meaning it should work for workers
and our newly added shadow realm global object by being stored on the
universal global scope mixin.
The MessagePort one in particular is required by Cloudflare Turnstile,
as the method it takes to run JS in a worker is to `eval` the contents
of `MessageEvent.data`. However, it will only do this if
`MessageEvent.isTrusted` is true, `MessageEvent.origin` is the empty
string and `MessageEvent.source` is `null`.
The Window version is a quick fix whilst in the vicinity, as its
MessageEvent should also be trusted.
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
The main motivation behind this is to remove JS specifics of the Realm
from the implementation of the Heap.
As a side effect of this change, this is a bit nicer to read than the
previous approach, and in my opinion, also makes it a little more clear
that this method is specific to a JavaScript Realm.
