This introduces 2 new machine operators that are variants of I64x2Splat
and I64x2ReplaceLane that takes two int32 operands instead of one i64
operand.

Bug: v8:9728
Change-Id: I6675f991e6c56821c84d183dacfda96961c1a708
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1841242Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64337}