It's no longer possible to fake built-in time zones using custom objects.
So testing DST shifts will have to use real built-in time zones. Replace
TemporalHelpers.springForwardFallBackTimeZone with America/Vancouver (it
was modelled on the DST transitions in 2000) and
TemporalHelpers.crossDateLineTimeZone with Pacific/Apia (it was modelled
on the 2011 switch to the other side of the international date line.)
These tests have to move to the intl402/ folder since non-Intl-aware
implementations are allowed (but not required) to support any built-in
time zones other than UTC.
This adds coverage for the situation where we get a different answer from
Temporal.Duration.compare depending on whether relativeTo resolves to a
PlainDate or ZonedDateTime.
See discussion in
https://github.com/tc39/test262/pull/3505#discussion_r859994610