[scoped-registry] Implement Initialize logic on scoped registry

Initialize function allows a node and its descendants with null scoped
registry be initialized with the given registry and used in future
upgrade/hydration.

Bug: 40826514
Change-Id: I4a5fc53a45310958919f10d9bb8d561a0df95966
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6832952
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Commit-Queue: Jayson Chen <jaysonchen@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1505439}