... for creating a FixedArray.
Calling builtins is generally cheaper than calling into the runtime, and
this also saves us a int->Smi conversion.
The builtin still has the "Wasm" prefix, since it's only used in wasm
for now.

R=thibaudm@chromium.org

Bug: v8:11453
Change-Id: I0c5b6b71ae1b07608f51e685014a0e8dc0034111
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2698674Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72839}