Temporarily Revert "[gicombiner] Add the MatchDag structure and parse...
Temporarily Revert "[gicombiner] Add the MatchDag structure and parse instruction DAG's from the input"
and follow-on patches.
This is breaking a few build bots and local builds with follow-up already
on the patch thread.
This reverts commits 390c8baa and
520e3d66.