Also move the responsibility of marking builtins as initialized
to the deserializer.

R=jkummerow@chromium.org

Review-Url: https://codereview.chromium.org/2840493002
Cr-Original-Commit-Position: refs/heads/master@{#44802}
Committed: https://chromium.googlesource.com/v8/v8/+/a2b3a2fbc562584ec298dfe674c97662a125a59e
Review-Url: https://codereview.chromium.org/2840493002
Cr-Commit-Position: refs/heads/master@{#44884}