This reverts commit ddd15cda.

Reason for revert: Blocks roll: https://chromium-review.googlesource.com/c/chromium/src/+/732565

Original change's description:
> [turbofan] Instance type tracking in load elimination.
> 
> This tracks instance type in load elimination, so that it can be used
> to prune control flow with unreachable states.
> 
> (This is a cut down version of https://chromium-review.googlesource.com/c/v8/v8/+/727761),
> the regression should be addressed by the map invalidation fix from
> https://chromium-review.googlesource.com/c/v8/v8/+/730705.)
> 
> Bug: v8:6396
> Change-Id: I3acab16ebbc0f1f16c7900a8d307deb84e1cb618
> Reviewed-on: https://chromium-review.googlesource.com/732307
> Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
> Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48812}

TBR=jarin@chromium.org,bmeurer@chromium.org

Change-Id: I1a3fe1d62c05889ea83e2f6cfb31a6ccbe65241d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6396
Reviewed-on: https://chromium-review.googlesource.com/732898Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Michael Hablich <hablich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48833}