This is a first step towards using Maps as store transition handlers.
It is expected for this CL to noticeably regress memory consumption
but most of it should be recovered by the next CL.

Bug: v8:5988
Change-Id: Ic2e301f9ccebc36e699383ded8c8cd284a906ce1
Reviewed-on: https://chromium-review.googlesource.com/928646
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51663}