This doesn't seem to provide any noticable performance wins, and just
adds more (generated) code. On a synthetic micro-benchmark for accessing
dictionary elements I was able to measure only a <1% difference for
loads and barely 1-2% for stores. That doesn't seem to be enough of a
reason to add four unrolled iterations of the lookup loop in all kinds
of places.

Bug: v8:5787, v8:8834
Change-Id: Iab8f71bf70a5518589ed4999a5be21d268ba1081
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1563774
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60770}