cmd/internal/obj/x86: add most missing AVX1/2 insts
This change applies x86avxgen output.
https://go-review.googlesource.com/c/arch/+/66972
As an effect, many new AVX instructions are now available.
One of the side-effects of this patch is
sorted AXXX (A-enum) constants.
Some AVX1/2 instructions still not added due to:
1. x86.csv V0.2 does not list them;
2. partially because of (1), test suite does not contain tests for
these instructions.