All we really need to expose is a single function that builds the graph.
This change drastically simplifies the header file.

Change-Id: If185687b8220bdd253f967be9ab2ea3b088e5423
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1585856Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61068}