[turbofan] Smartify the GraphReducer.
Don't use the generic algorithm, but instead start going into the
direction of ControlReducer, using a stack plus a revisit queue to
not miss any more possibilities for reductions anymore.
TEST=cctest,unittests
R=dcarney@chromium.org
Committed: https://chromium.googlesource.com/v8/v8/+/
f047507370634155113d78685372630a230613cf
Committed: https://chromium.googlesource.com/v8/v8/+/
6e148989a4227a5290a7f8ca72c71f5740870afe
Review URL: https://codereview.chromium.org/
726513002
Cr-Commit-Position: refs/heads/master@{#25377}