Port 9fcbb5e3

Original Commit Message:

    Replace unsigned extract lane followed by sign extend
    as added here https://chromium-review.googlesource.com/c/v8/v8/+/1846711
    with a signed extract lane for I8x16 and I16x8.

R=george.wort@arm.com, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I09254621c45298a431da44cc1670a90c7a8add0b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1949062Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#65316}