Also removes a few leftover TODOs and scraps of commented-out code
from simd development.
Updated etetest.sh to make it behave whether amd64 implies the
experiment, or not.
Fixes#76473.
Change-Id: I6d9792214d7f514cb90c21b101dbf7d07c1d0e55
Reviewed-on: https://go-review.googlesource.com/c/go/+/728220
TryBot-Bypass: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>