[turbofan] Connect loops to end via Terminate during graph building.

[turbofan] Connect loops to end via Terminate during graph building.

This way we don't need to connect (potentially) non-terminating loops
later during control reduction, which saves one forward pass over the
control graph.  Long term we will move the trimming functionality of
the control reducer to the GraphReducer, and get rid of the Finish
method again.

As a bonus, this change also properly rewires Terminate, Throw and
Deoptimize during inlining.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1155683004

Cr-Commit-Position: refs/heads/master@{#28625}