This is a reland of 00babf07

No changes from original patch, previous CQ failures were likely
a Mac infra issue https://chromium-review.googlesource.com/c/2682521.

Original change's description:
> [wasm-simd][x64][liftoff] Implement i8x16.popcnt
>
> Extract i8x16.popcnt implementation into a macro-assembler function, and
> reuse it in Liftoff.
>
> Bug: v8:11002
> Change-Id: I86b2f5322c799d44f584cac28c70e0e393bf114f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2676280
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
> Commit-Queue: Zhi An Ng <zhin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#72565}

Bug: v8:11002
Change-Id: Ic8bcbdb3444865805d8d2af3669ccb4a05c4426d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2682507Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72614}