Split IANA timezone test from built-ins to intl402

Author: Jack-Works

test/built-ins/Temporal/Duration/prototype/round/rounding-increment-relativeto.js

@@ -39,8 +39,3 @@ TemporalHelpers.assertDuration(new Temporal.Duration(0, 1, 0, 30).round({
   roundingIncrement: 2,
   relativeTo: new Temporal.PlainDate(1970, 7, 31)
 }), 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, `1m30d to 2m with relativeTo 1970-07-31`);
-TemporalHelpers.assertDuration(new Temporal.Duration(0, 1, 0, 30).round({
-  smallestUnit: "months",
-  roundingIncrement: 2,
-  relativeTo: Temporal.ZonedDateTime.from('2025-03-09T03:00:00-07:00[America/Vancouver]')
-}), 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, `1m30d to 2m with relativeTo 2025-03-09T03:00:00-07:00[America/Vancouver]`);

test/intl402/Temporal/Duration/prototype/round/rounding-increment-relativeto.js

@@ -0,0 +1,16 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Test a specific buggy case from temporal_rs
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const relativeTo = Temporal.ZonedDateTime.from('2025-03-09T03:00:00-07:00[America/Vancouver]');
+TemporalHelpers.assertDuration(new Temporal.Duration(0, 1, 0, 30).round({
+  smallestUnit: "months",
+  roundingIncrement: 2,
+  relativeTo,
+}), 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, `1m30d to 2m with relativeTo 2025-03-09T03:00:00-07:00[America/Vancouver]`);