The gist is that we need to construct an ICU date-time formatter for
each possible Temporal type. This is of course going to be expensive.
So instead, we construct the configurations needed for the ICU objects
in the Intl.DateTimeFormat constructor, and defer creating the actual
ICU objects until they are needed.
Each formatting prototype can also now accept either a number (as they
already did), or any of the supported Temporal objects. These types may
not be mixed, and their properties (namely, their calendar) must align
with the Intl.DateTimeFormat object.
We now have the Temporal facilities to implement the Date AOs which
parse UTC offset strings using the ISO8601 parser. This patch updates
those AOs and their callers in accordance with the Temporal spec.
The Duration record no longer exists in Temporal. Implement it according
to the DurationFormat spec to prepare for its removal from our Temporal
implementation.
We also implement the DurationSign AO here as well, as the Temporal
implementation will now require a Temporal.Duration JS object.
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.
