TracedNode is used as backing node for v8::TracedGlobal (with
destructor) and v8::TracedReference (no destructor).

A future change adds concurrent marking for TracedReference which
requires that the node stays around until the atomic pause to avoid
synchronization with the concurrent marker.

This change prepares TracedNode in prolonging the lifetime until the
it is actively cleared ("sweeped") in the atomic pause. This allows
for spuriously keeping alive a TracedNode for an additional GC cycle
in the case the the node was destroyed while the marker is running.

We maintain eager clearing of nodes where possible, i.e., outside of
incremental marking.

Bug: v8:12600
Change-Id: I9688c83a42b70d352c84613485f37242b1b910a6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3436805Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78947}