Port 4f6ba385

Original Commit Message:

    This is a reland of de88bfb2

    Original change's description:
    > [wasm-simd] Implement remaining I8x16 SIMD ops on x64
    >
    >  - Implementation for I8x16 Shifts, and Mul
    >  - Fix convert bug
    >  - Enable all tests except for shuffle tests
    >
    > Change-Id: Id1a469d2883c30ea782c51d21dc462d211f94420
    > Reviewed-on: https://chromium-review.googlesource.com/c/1318609
    > Reviewed-by: Bill Budge <bbudge@chromium.org>
    > Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#57254}

R=gdeepti@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I18980c8844a3e859b4ca3f2181de9f337bfb9698
Reviewed-on: https://chromium-review.googlesource.com/c/1324269Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#57333}