conf: Introduce support for 'hv-avic' Hyper-V enlightenment

qemu-6.2 introduced support for the hv-avic enlightenment which allows
to use Hyper-V SynIC with hardware APICv/AVIC enabled.

Implement the libvirt support for it.

Closes: https://gitlab.com/libvirt/libvirt/-/issues/402
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

tests/qemuxml2argvdata/hyperv.x86_64-latest.args

@@ -12,7 +12,7 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
 -object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/tmp/lib/domain--1-QEMUGuest1/master-key.aes"}' \
 -machine pc,usb=off,dump-guest-core=off,memory-backend=pc.ram \
 -accel tcg \
--cpu 'qemu64,hv-relaxed=on,hv-vapic=on,hv-spinlocks=0x2fff,hv-vpindex=on,hv-runtime=on,hv-synic=on,hv-stimer=on,hv-reset=on,hv-vendor-id=KVM Hv,hv-frequencies=on,hv-reenlightenment=on,hv-tlbflush=on,hv-ipi=on,hv-evmcs=on' \
+-cpu 'qemu64,hv-relaxed=on,hv-vapic=on,hv-spinlocks=0x2fff,hv-vpindex=on,hv-runtime=on,hv-synic=on,hv-stimer=on,hv-reset=on,hv-vendor-id=KVM Hv,hv-frequencies=on,hv-reenlightenment=on,hv-tlbflush=on,hv-ipi=on,hv-evmcs=on,hv-avic=on' \
 -m 214 \
 -object '{"qom-type":"memory-backend-ram","id":"pc.ram","size":224395264}' \
 -overcommit mem-lock=off \

tests/qemuxml2argvdata/hyperv.xml

@@ -25,6 +25,7 @@
       <tlbflush state='on'/>
       <ipi state='on'/>
       <evmcs state='on'/>
+      <avic state='on'/>
     </hyperv>
   </features>
   <clock offset='utc'/>