This is a reland of 306bb635

Original change's description:
> [wasm-simd] Implement F64x2ConvertI64x2 for x64
> 
> Bug: v8:8460
> Change-Id: Icefb90c67af77ac93bd75b4e452ba426232de83a
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1710332
> Commit-Queue: Zhi An Ng <zhin@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Bill Budge <bbudge@chromium.org>
> Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#63627}

Bug: v8:8460
Change-Id: I08d2c88e81ce51d3d1cfdf3d7d6ba34792e34e9e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1793902Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64365}