This reverts commit 43b885a8.

Reason for revert: Still fails on UBSan: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20UBSan/10873

Original change's description:
> Reland "[turbofan][csa] optimize Smi untagging better"
> 
> This is a reland of ff22ae80
> 
> Original change's description:
> > [turbofan][csa] optimize Smi untagging better
> > 
> > - Introduce new operator variants for signed right-shifts with the
> >   additional information that they always shift out zeros.
> > - Use these new operators for Smi untagging.
> > - Merge left-shifts with a preceding Smi-untagging shift.
> > - Optimize comparisons of Smi-untagging shifts to operate on the
> >   unshifted word.
> > - Optimize 64bit comparisons of values expanded from 32bit to use
> >   a 32bit comparison instead.
> > - Change CodeStubAssembler::UntagSmi to first sign-extend and then
> >   right-shift to enable better address computations for Smi indices.
> > 
> > Bug: v8:9962
> > Change-Id: If91300f365e8f01457aebf0bd43bdf88b305c460
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2135734
> > Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> > Reviewed-by: Georg Neis <neis@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#67378}
> 
> Bug: v8:9962
> Change-Id: Ieab0755806c95fb50022eb17596fb0c95f36004c
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2170001
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Commit-Queue: Georg Neis <neis@chromium.org>
> Auto-Submit: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67430}

TBR=neis@chromium.org,tebbi@chromium.org

Change-Id: I49e19811ebcecb846f61291bc0c4a0d8b0bc4cff
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:9962
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2168876Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67431}