hyperv: Add support to process syndbg commands

SynDbg commands can come from two different flows:
1. Hypercalls, in this mode the data being sent is fully
   encapsulated network packets.
2. SynDbg specific MSRs, in this mode only the data that needs to be
   transfered is passed.

Signed-off-by: Jon Doron <arilou@gmail.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220216102500.692781-4-arilou@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>