Add internal create operations to avoid observable effects

The constructors of PlainDate, PlainDateTime, PlainMonthDay,
PlainYearMonth, and ZonedDateTime call ToTemporalCalendar on the calendar
argument, and the constructor of ZonedDateTime additionally calls
ToTemporalTimeZone on its timeZone argument. Now that these operations
include an observable HasProperty operation, we do not want to call them
more than once on the same calendar or time zone object.

Therefore we add CreateTemporalDate etc. which create an instance without
any observable validation of the arguments.

The spec text already works like this, with abstract operations such as
CreateTemporalZonedDateTime and friends that do not call
ToTemporalCalendar or ToTemporalTimeZone. So this is not a normative
change; it's a compliance bug in the polyfill. It is required for the
test262 tests in 19cd26f to pass, which observe HasProperty(`timeZone`)
operations.

See: #1428

polyfill/lib/calendar.mjs

@@ -179,17 +179,15 @@ impl['iso8601'] = {
     fields = resolveNonLunisolarMonth(fields);
     let { year, month, day } = fields;
     ({ year, month, day } = ES.RegulateISODate(year, month, day, overflow));
-    const TemporalPlainDate = GetIntrinsic('%Temporal.PlainDate%');
-    return new TemporalPlainDate(year, month, day, calendar);
+    return ES.CreateTemporalDate(year, month, day, calendar);
   },
   yearMonthFromFields(fields, options, calendar) {
     const overflow = ES.ToTemporalOverflow(options);
     fields = ES.PrepareTemporalFields(fields, [['month', undefined], ['monthCode', undefined], ['year']]);
     fields = resolveNonLunisolarMonth(fields);
     let { year, month } = fields;
     ({ year, month } = ES.RegulateISOYearMonth(year, month, overflow));
-    const TemporalPlainYearMonth = GetIntrinsic('%Temporal.PlainYearMonth%');
-    return new TemporalPlainYearMonth(year, month, calendar, /* referenceISODay */ 1);
+    return ES.CreateTemporalYearMonth(year, month, calendar, /* referenceISODay = */ 1);
   },
   monthDayFromFields(fields, options, calendar) {
     const overflow = ES.ToTemporalOverflow(options);
@@ -207,8 +205,7 @@ impl['iso8601'] = {
     fields = resolveNonLunisolarMonth(fields);
     let { month, day, year } = fields;
     ({ month, day } = ES.RegulateISODate(useYear ? year : referenceISOYear, month, day, overflow));
-    const TemporalPlainMonthDay = GetIntrinsic('%Temporal.PlainMonthDay%');
-    return new TemporalPlainMonthDay(month, day, calendar, referenceISOYear);
+    return ES.CreateTemporalMonthDay(month, day, calendar, referenceISOYear);
   },
   fields(fields) {
     return fields;
@@ -228,8 +225,7 @@ impl['iso8601'] = {
     let month = GetSlot(date, ISO_MONTH);
     let day = GetSlot(date, ISO_DAY);
     ({ year, month, day } = ES.AddISODate(year, month, day, years, months, weeks, days, overflow));
-    const TemporalPlainDate = GetIntrinsic('%Temporal.PlainDate%');
-    return new TemporalPlainDate(year, month, day, calendar);
+    return ES.CreateTemporalDate(year, month, day, calendar);
   },
   dateUntil(one, two, largestUnit) {
     return ES.DifferenceISODate(
@@ -1782,8 +1778,7 @@ const nonIsoGeneralImpl = {
       ['year', undefined]
     ]);
     const { year, month, day } = this.helper.calendarToIsoDate(fields, overflow, cache);
-    const TemporalPlainDate = GetIntrinsic('%Temporal.PlainDate%');
-    const result = new TemporalPlainDate(year, month, day, calendar);
+    const result = ES.CreateTemporalDate(year, month, day, calendar);
     cache.setObject(result);
     return result;
   },
@@ -1799,8 +1794,7 @@ const nonIsoGeneralImpl = {
       ['year', undefined]
     ]);
     const { year, month, day } = this.helper.calendarToIsoDate({ ...fields, day: 1 }, overflow, cache);
-    const TemporalPlainYearMonth = GetIntrinsic('%Temporal.PlainYearMonth%');
-    const result = new TemporalPlainYearMonth(year, month, calendar, /* referenceISODay = */ day);
+    const result = ES.CreateTemporalYearMonth(year, month, calendar, /* referenceISODay = */ day);
     cache.setObject(result);
     return result;
   },
@@ -1821,8 +1815,7 @@ const nonIsoGeneralImpl = {
     ]);
     const { year, month, day } = this.helper.monthDayFromFields(fields, overflow, cache);
     // `year` is a reference year where this month/day exists in this calendar
-    const TemporalPlainMonthDay = GetIntrinsic('%Temporal.PlainMonthDay%');
-    const result = new TemporalPlainMonthDay(month, day, calendar, /* referenceISOYear */ year);
+    const result = ES.CreateTemporalMonthDay(month, day, calendar, /* referenceISOYear = */ year);
     cache.setObject(result);
     return result;
   },
@@ -1857,8 +1850,7 @@ const nonIsoGeneralImpl = {
     const added = this.helper.addCalendar(calendarDate, { years, months, weeks, days }, overflow, cache);
     const isoAdded = this.helper.calendarToIsoDate(added, 'constrain', cache);
     const { year, month, day } = isoAdded;
-    const TemporalPlainDate = GetIntrinsic('%Temporal.PlainDate%');
-    const newTemporalObject = new TemporalPlainDate(year, month, day, calendar);
+    const newTemporalObject = ES.CreateTemporalDate(year, month, day, calendar);
     // The new object's cache starts with the cache of the old object
     const newCache = new OneObjectCache(cache);
     newCache.setObject(newTemporalObject);