Reorder deserialization steps: instead of processing functions one by
one, run each step individually on all functions (read & allocate, copy
& relocate, publish). This prepares for moving some steps to background
tasks.

R=ahaas@chromium.org
CC=clemensb@chromium.org

Bug: v8:11164
Change-Id: Ic6e1e387b6a60ab16efc91f8e0d45cb2acded2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2543929
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71288}