JS nodes that are connected to C++ nodes are merged with them in the
snapshot.

Bug: chromium:1056170
Change-Id: I137a21b3d847e669bf65962224050f5402bcff7c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2951732Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75080}