This CL provides the minimum necessary functionality to expose fast API
for testing in mjsunit, exposing the fast path for fuzzing. It exposes
a d8.test.fast_c_api with an `add_all` method, which exercises primitive
types. On x64, all integer and floating point types are supported. On
other platforms currently only 32-bit integers are included in the test.

Design doc:
https://docs.google.com/document/d/1KUKPfXkSRZTA2gMwaWbpQKlYfw0C-T6AE3XzC4viHbo/

Bug: chromium:1052746
Change-Id: Icc824199a26dd2abd2b869f5483a39d38e4dce3e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2749154Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73670}