Fix observable call of ToRelativeTemporalObject in Duration.p.total

The reference code was out of line with the spec text here, which says
that ToRelativeTemporalObject must be called before GetTemporalUnit. Both
calls are observable.

See also tc39/proposal-temporal#2252

UPSTREAM_COMMIT=5644cbd89a65cd4264c80e59c03c7bdea06f4821

Author: ptomato

lib/duration.ts

@@ -334,8 +334,8 @@ export class Duration implements Temporal.Duration {
       typeof optionsParam === 'string'
         ? (ES.CreateOnePropObject('unit', optionsParam) as Exclude<typeof optionsParam, string>)
         : ES.GetOptionsObject(optionsParam);
-    const unit = ES.GetTemporalUnit(options, 'unit', 'datetime', ES.REQUIRED);
     const relativeTo = ES.ToRelativeTemporalObject(options);
+    const unit = ES.GetTemporalUnit(options, 'unit', 'datetime', ES.REQUIRED);
 
     // Convert larger units down to days
     ({ years, months, weeks, days } = ES.UnbalanceDurationRelative(years, months, weeks, days, unit, relativeTo));