libvirt: support memory failure event

libvirt: support memory failure event

Introduce memory failure event. Libvirt should monitor domain's
event, then posts it to uplayer. According to the hardware memory
corrupted message, a cloud scheduler could migrate domain to another
health physical server.

Several changes in this patch:
public API:
    include/*
    src/conf/*
    src/remote/*
    src/remote_protocol-structs

client:
    examples/c/misc/event-test.c
    tools/virsh-domain.c

With this patch, each driver could implement its own method to run
this new event.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>