cpu_map: Add support for arch-capabilities feature

cpu_map: Add support for arch-capabilities feature

The feature was added to QEMU in 3.1.0 and it is currently blocking
migration, which is expected to change in the future. Luckily 3.1.0 is
new enough to give us migratability hints on each feature via
query-cpu-model-expension, which means we don't need to use the
"migratable" attribute on the CPU map XML.

The kernel calls this feature arch_capabilities and RHEL/CentOS 7.* use
arch-facilities. Apparently some CPU test files were gathered with the
RHEL version of QEMU. Let's update the test files to avoid possible
confusion about the correct naming.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>