xen/vm-events: Move parts of monitor_domctl code to common-side.

xen/vm-events: Move parts of monitor_domctl code to common-side.

This patch moves monitor_domctl to common-side.
Purpose: move what's common to common, prepare for implementation
of such vm-events on ARM.

* move get_capabilities to arch-side => arch_monitor_get_capabilities.
* add arch-side monitor op handling function => arch_monitor_domctl_op.
  e.g. X86-side handles XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP op
* add arch-side monitor event handling function => arch_monitor_domctl_event.
  e.g. X86-side handles XEN_DOMCTL_MONITOR_EVENT_MOV_TO_MSR event enable/disable
* remove status_check

Signed-off-by: Corneliu ZUZU <czuzu@bitdefender.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Razvan Cojocaru <rcojocaru@bitdefender.com>