This CL introduces new FixedArray subclasses that behave like
fixed-sized arrays of integers. Under the hood, these are just
ByteArrays with integer element accessors.

These new classes will be used in follow-up CLs which moves various
integer arrays from the native heap onto the V8 heap.

Bug: chromium:1335046
Change-Id: Ie7497b4464c1a037e4eaf49e8bf7ac4da62512de
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3838775Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Linke <jgruber@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82678}