This also includes a stubbed Temporal.Duration.prototype.
Until we have re-implemented Temporal.PlainDate/ZonedDateTime, some of
Temporal.Duration.compare (and its invoked AOs) are left unimplemented.
Our Temporal implementation is woefully out of date. The spec has been
so vastly rewritten that it is unfortunately not practical to update our
implementation in-place. Even just removing Temporal objects that were
removed from the spec, or updating any of the simpler remaining objects,
has proven to be a mess in previous attempts.
So, this removes our Temporal implementation. AOs used by other specs
are left intact.
