- Fix copying of already initialized nodes
- Add better verification
- Add tests for moving/copying onto already initialized nodes

Bug: chromium:1040038
Change-Id: I0c144fcfe980d7542cf6803e4dc861e3fd4ca708
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2007278Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65858}