This CL takes advantage of the z15 `load reverse and replicate`
instruction to optimize Simd LoadSplat opcodes.

On the simulator we only run `load replicate` as reversing is
not required.

We will need to implement the rest of the `load transform` ops
before enabling this from wasm-compiler on BE machines.

Change-Id: I81ffedf51c3d35dbbc2a6455a2756cad25434127
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3115142Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#76490}