In {ControlPathState} with {kMultipleInstances}, a node should be able
to be mapped to different states, but not twice to an identical state.

Change-Id: Ida340a6f4f5e891f586d5a90e7ae818f24dfbe98
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3769693
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81775}