qemu: Use full CPU model expansion on x86

qemu: Use full CPU model expansion on x86

The static CPU model expansion is designed to return only canonical
names of all CPU properties. To maintain backwards compatibility libvirt
is stuck with different spelling of some of the features, but we need to
use the full expansion to get the additional spellings. In addition to
returning all spelling variants for all properties the full expansion
will contain properties which are not guaranteed to be migration
compatible. Thus, we need to combine both expansions. First we need to
call the static expansion to limit the result to migratable properties.
Then we can use the result of the static expansion as an input to the
full expansion to get both canonical names and their aliases.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>