Add test for DST balancing

References:

+ tc39/proposal-temporal#1791

Thanks @ptomato for the suggestion to use
`springForwardFallBackTimeZone`.

test/built-ins/Temporal/Duration/compare/twenty-five-hour-day.js

@@ -0,0 +1,33 @@
+// 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.duration.compare
+description: Unbalancing handles DST days with more than hours
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tz = TemporalHelpers.springForwardFallBackTimeZone();
+
+// 2000-10-29 is a 25-hour day according to this time zone...
+
+const relativeTo = new Temporal.ZonedDateTime(941187600_000_000_000n, tz);
+
+// confirm that we have rewound one year and one day:
+assert.sameValue('1999-10-29T01:00:00-08:00[Custom/Spring_Fall]', relativeTo.toString());
+
+const d1 = new Temporal.Duration(1, 0, 0, 1);
+const d2 = new Temporal.Duration(1, 0, 0, 0, 25);
+
+// ...so the durations should be equal relative to relativeTo:
+
+assert.sameValue(0,
+  Temporal.Duration.compare(d1, d2, { relativeTo }),
+  "2000-10-29 is a 25-hour day"
+);
+
+assert.sameValue(1,
+  Temporal.Duration.compare(d1, { years: 1, hours: 24 }, { relativeTo }),
+  "2020-10-29 has more than 24 hours"
+);