[web snapshot] Pass exports to the serializer as a Local<PrimitiveArray>

This CL updates WebSnapshotSerializer::TakeSnapshot() to accept exports
as a Local<PrimitiveArray>.

Bug: v8:11525, v8:11706
Change-Id: Ie3a752ac7dbcc51fc4fb258eb44ce42d0cfc6a0f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2930173


Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Vicky Kontoura <vkont@google.com>
Cr-Commit-Position: refs/heads/master@{#74936}