It turns out that KeyAccumulator::GetKeys will fail if the object it is
operating on is a Proxy with an ownKeys() or getOwnPropertyDescriptor()
trap that throws. Handle this case in
Isolate::GetImportAssertionsFromArgument by bailing out early.

Bug: v8:11730
Change-Id: I363bf2d218f6ba7eeb2001cd644f5529901fdb3e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2875541Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Dan Clark <daniec@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#74417}