Short-circuit common case of comparing a calendar or time zone to itself

In CalendarEquals, TimeZoneEquals, and ConsolidateCalendars, remove the
observable toString() calls from the path where both calendars are the
same object.

See: #1425

polyfill/lib/ecmascript.mjs

@@ -1844,11 +1844,13 @@ export const ES = ObjectAssign({}, ES2020, {
     return cal1 < cal2 ? -1 : cal1 > cal2 ? 1 : 0;
   },
   CalendarEquals: (one, two) => {
+    if (one === two) return true;
     const cal1 = ES.ToString(one);
     const cal2 = ES.ToString(two);
     return cal1 === cal2;
   },
   ConsolidateCalendars: (one, two) => {
+    if (one === two) return two;
     const sOne = ES.ToString(one);
     const sTwo = ES.ToString(two);
     if (sOne === sTwo || sOne === 'iso8601') {
@@ -1893,6 +1895,7 @@ export const ES = ObjectAssign({}, ES2020, {
     return new TemporalTimeZone(timeZone);
   },
   TimeZoneEquals: (one, two) => {
+    if (one === two) return true;
     const tz1 = ES.ToString(one);
     const tz2 = ES.ToString(two);
     return tz1 === tz2;

spec/calendar.html

@@ -329,6 +329,7 @@ <h1>FormatCalendarAnnotation ( _id_, _showCalendar_ )</h1>
     <emu-clause id="sec-temporal-calendarequals" aoid="CalendarEquals">
       <h1>CalendarEquals ( _one_, _two_ )</h1>
       <emu-alg>
+        1. If _one_ and _two_ are the same Object value, return *true*.
         1. Let _calendarOne_ be ? ToString(_one_).
         1. Let _calendarTwo_ be ? ToString(_two_).
         1. If _calendarOne_ is _calendarTwo_, return *true*.
@@ -339,6 +340,7 @@ <h1>CalendarEquals ( _one_, _two_ )</h1>
     <emu-clause id="sec-temporal-consolidatecalendars" aoid="ConsolidateCalendars">
       <h1>ConsolidateCalendars ( _one_, _two_ )</h1>
       <emu-alg>
+        1. If _one_ and _two_ are the same Object value, return _two_.
         1. Let _calendarOne_ be ? ToString(_one_).
         1. Let _calendarTwo_ be ? ToString(_two_).
         1. If _calendarOne_ is _calendarTwo_, return _two_.

spec/timezone.html

@@ -640,6 +640,7 @@ <h1>TimeZoneEquals ( _one_, _two_ )</h1>
         calling `toString()` on its arguments are equal.
       </p>
       <emu-alg>
+        1. If _one_ and _two_ are the same Object value, return *true*.
         1. Let _timeZoneOne_ be ? ToString(_one_).
         1. Let _timeZoneTwo_ be ? ToString(_two_).
         1. If _timeZoneOne_ is _timeZoneTwo_, return *true*.