vfio-user: define vfio-user-server object

vfio-user: define vfio-user-server object

Define vfio-user object which is remote process server for QEMU. Setup
object initialization functions and properties necessary to instantiate
the object

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: e45a17001e9b38f451543a664ababdf860e5f2f2.1655151679.git.jag.raman@oracle.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>