Temporal: Test that the offset option has the last word in ZDT.from()

The programmer always gets the last word over how the string is
interpreted, since otherwise it's not possible to make any guarantees
about the offset option. (This is the "out-of-band" mechanism mentioned in
the IETF draft.) Add a test for this.

test/built-ins/Temporal/ZonedDateTime/from/offset-overrides-critical-flag.js

@@ -0,0 +1,30 @@
+// 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.zoneddatetime.from
+description: >
+  The offset option always overrides the critical flag in a time zone annotation
+features: [Temporal]
+---*/
+
+const useResult = Temporal.ZonedDateTime.from("2022-10-07T18:37-07:00[!UTC]", { offset: "use" });
+assert.sameValue(
+  useResult.epochNanoseconds,
+  1665193020000000000n,
+  "exact time is unchanged with offset = use, despite critical flag"
+);
+
+const ignoreResult = Temporal.ZonedDateTime.from("2022-10-07T18:37-07:00[!UTC]", { offset: "ignore" });
+assert.sameValue(
+  ignoreResult.epochNanoseconds,
+  1665167820000000000n,
+  "wall time is unchanged with offset = ignore, despite critical flag"
+);
+
+const preferResult = Temporal.ZonedDateTime.from("2022-10-07T18:37-07:00[!UTC]", { offset: "prefer" });
+assert.sameValue(
+  useResult.epochNanoseconds,
+  1665193020000000000n,
+  "offset is recalculated with offset = prefer, despite critical flag"
+);