Polyfill: Implement DurationFormat.p.format{,ToParts} accepting Duration

An additional modification to ECMA-402 that Temporal makes, is for
DurationFormat.p.format and formatToParts to accept a Temporal.Duration
object as input. This monkeypatches those methods to conform to that
requirement.

polyfill/lib/intl.mjs

@@ -16,6 +16,7 @@ import {
   IntlDateTimeFormatPrototypeResolvedOptions,
   IntlDurationFormatPrototype,
   IntlDurationFormatPrototypeFormat,
+  IntlDurationFormatPrototypeFormatToParts,
   IntlDurationFormatPrototypeResolvedOptions,
   ObjectAssign,
   ObjectCreate,
@@ -667,3 +668,13 @@ export function ModifiedIntlDurationFormatPrototypeFormat(durationLike) {
   const record = temporalDurationToCompatibilityRecord(duration);
   return ES.Call(IntlDurationFormatPrototypeFormat, this, [record]);
 }
+
+if (IntlDurationFormatPrototype) {
+  IntlDurationFormatPrototype.format = ModifiedIntlDurationFormatPrototypeFormat;
+  IntlDurationFormatPrototype.formatToParts = function formatToParts(durationLike) {
+    ES.Call(IntlDurationFormatPrototypeResolvedOptions, this); // brand check
+    const duration = ES.ToTemporalDuration(durationLike);
+    const record = temporalDurationToCompatibilityRecord(duration);
+    return ES.Call(IntlDurationFormatPrototypeFormatToParts, this, [record]);
+  };
+}

polyfill/lib/primordials.mjs

@@ -96,6 +96,7 @@ export const {
 export const IntlDurationFormatPrototype = IntlDurationFormat?.prototype ?? ObjectCreate(null);
 export const {
   format: IntlDurationFormatPrototypeFormat,
+  formatToParts: IntlDurationFormatPrototypeFormatToParts,
   resolvedOptions: IntlDurationFormatPrototypeResolvedOptions
 } = IntlDurationFormatPrototype;
 export const { stringify: JSONStringify } = JSON;