This is mainly a torque change, but as a drive-by we get rid of
kStartOfPointerFieldsOffset
kEndOfTaggedFieldsOffset
which often are used to enclose a section of pointers in an object.

Bug: v8:7793
Change-Id: I52d83d09249a3cc6a99e7e7506e154ccfca53a12
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1615249
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61722}