Also add the first intrinsic and usage of it: %RawCast

Bug: v8:7793
Change-Id: Id1e3288e8bab6adb510731076a39590e8fd156be
Reviewed-on: https://chromium-review.googlesource.com/c/1344152
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57692}