Temporal: Test Calendar.p.mergeFields enumeration changes

This tests the normative changes in
https://github.com/tc39/proposal-temporal/pull/2245, which achieved
consensus in the July 2022 TC39 meeting, specifically as they apply to the
Temporal.Calendar.prototype.mergeFields method.

Due to the use of the pre-existing spec operation CopyDataProperties, now
symbol keys are merged into the return value, and the order of observable
property operations has changed from a batch of [[GetOwnProperty]]
followed by a batch of [[Get]], to a series of interleaved
[[GetOwnProperty]]/[[Get]] pairs.

test/built-ins/Temporal/Calendar/prototype/mergeFields/non-string-properties.js

@@ -4,7 +4,7 @@
 
 /*---
 esid: sec-temporal.calendar.prototype.mergefields
-description: Only string keys from the arguments are merged
+description: Both string and symbol keys from the arguments are merged
 info: |
   1. Let calendar be the this value.
   2. Perform ? RequireInternalSlot(calendar, [[InitializedTemporalCalendar]]).
@@ -50,6 +50,6 @@ const foo = Symbol("foo");
 const bar = Symbol("bar");
 assertEntriesEqual(
   cal.mergeFields({ [foo]: 1 }, { [bar]: 2 }),
-  [],
+  [[foo, 1], [bar, 2]],
-  "symbol keys are not merged"
+  "symbol keys are also merged"
 );

test/built-ins/Temporal/Calendar/prototype/mergeFields/order-of-operations.js

@@ -0,0 +1,45 @@
+// Copyright (C) 2022 Igalia S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.mergefields
+description: Properties on objects passed to mergeFields() are accessed in the correct order
+features: [Temporal]
+includes: [compareArray.js, temporalHelpers.js]
+---*/
+
+const expected = [
+  "ownKeys fields",
+  "getOwnPropertyDescriptor fields.year",
+  "get fields.year",
+  "getOwnPropertyDescriptor fields.month",
+  "get fields.month",
+  "getOwnPropertyDescriptor fields.day",
+  "get fields.day",
+  "getOwnPropertyDescriptor fields.extra",
+  "get fields.extra",
+  "ownKeys additionalFields",
+  "getOwnPropertyDescriptor additionalFields.3",
+  "get additionalFields.3",
+  "getOwnPropertyDescriptor additionalFields.monthCode",
+  "get additionalFields.monthCode",
+  "getOwnPropertyDescriptor additionalFields[Symbol('extra')]",
+  "get additionalFields[Symbol('extra')]",
+];
+const actual = [];
+
+const fields = TemporalHelpers.propertyBagObserver(actual, {
+  year: 2022,
+  month: 10,
+  day: 17,
+  extra: "extra property",
+}, "fields");
+const additionalFields = TemporalHelpers.propertyBagObserver(actual, {
+  [Symbol("extra")]: "extra symbol property",
+  monthCode: "M10",
+  3: "extra array index property",
+}, "additionalFields");
+
+const instance = new Temporal.Calendar("iso8601");
+instance.mergeFields(fields, additionalFields);
+assert.compareArray(actual, expected, "order of observable operations");