x86emul: support of AVX512* population count insns

x86emul: support of AVX512* population count insns

Plus the only other AVX512_BITALG one.

As in a few cases before, since the insns here and in particular their
memory access patterns follow the usual scheme, I didn't think it was
necessary to add a contrived test specifically for them, beyond the
Disp8 scaling one.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>