This CL implements i8x16.extract_lane_u, i16x8.extract_lane_u operations by
changing the default narrow extract operations to be unsigned. The
sign-extended extracts are implemented on top of the unsigned extracts
with an additional extend compiler node.
For IA32/X64, the codegen effectively remains the same -

0x389332bc32a3    63  660f3a14c900   pextrb rcx,xmm1,0
0x389332bc32a9    69  0fbec9         movsxbl rcx,rcx

0x389332bc32a3    63  660f3a14c900   pextrb rcx,xmm1,0
0x389332bc32a9    69  0fbec9         movsxbl rcx,rcx

On ARM, this adds an additional sxt instruction for the signed extracts.

Bug: v8:8460
Change-Id: I67f14b2b860ff8cc86ffbb2f65c7ef7de32da83f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1846711Reviewed-by: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64172}