qemu_capabilities: Report Hyper-V Enlightenments in domcapabilities

qemu_capabilities: Report Hyper-V Enlightenments in domcapabilities

Inside of qemuCaps (for the corresponding accelerator) we have
full host CPU expansion stored, among with supported Hyper-V
Enlightenments. To report them in the domain capabilities, we
just have to pick those starting with "hv-" and see if we know
them.

You may notice that neither of our domaincapsdata test shows any
enlightenment. This is because the test works by parsing
corresponding qemucapabilitiesdata/caps_*.xml file and none of
these store the full host CPU expansion (hostCPU.fullQEMU)
because that is runtime piece of information and not formatted
into virQEMUCaps XML.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1717611
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>