The refactoring makes it explicit that a v8::Array results in a
protocol::ListValue, and a v8::Object in a protocol::DictionaryValue,
which will be useful in a follow-up.

Bug: chromium:1213393
Change-Id: I0d6e5b013a828e12cb3200672d4fd9b14a14a807
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2919831Reviewed-by: Philip Pfaffe <pfaffe@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74839}