[dev.simd] simd: attempting to pin down the simdgen output-order glitch

Found one place where input order *might* affect other
order (type maps) and normalized there.

Added a gratuitous shuffle before sorting, in an attempt
to smoke out any problems in the sort order; none were
found, but left it in just to help quickly reveal future
problems.

Change-Id: I26c01c8ff244af15b05564d0441afe259a0edbea
Reviewed-on: https://go-review.googlesource.com/c/go/+/785580
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>