Remove the separate Initialize method from Deserializer, opting instead
to pass around SnapshotData where appropriate and pass the isolate
directly into the Deserializer's constructor.

Change-Id: I0092fadd9c81f14b2ce75145fd81af37c3947c65
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2448466
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70310}