This is a reland of a3b1233e

Changes compared to original commit:
- Use a more canonical way to replace TrapIf/Unless nodes that always
  trap. This fixes the issue where their outputs were marked dead even
  if they were Merge/Loop nodes.
- Use Throw() over Return() to connect a dangling trap to End().
- Add regression test.

Original change's description:
> [turbofan] Optimize TrapIf/Unless in BranchElim. and CommonOp-Reducer
>
> Bug: v8:11510
> Change-Id: I1e8fcb54444e494c7d765ad556d09d954441361f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2752876
> Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#73468}

Bug: v8:11510, chromium:1189454
Change-Id: I1d691a3ea299ed668cff925910ed231aad37cac6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2772601
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73537}