runtime-rs: Name vhost-user-net devices like the other backends

The virtio-net and vhost-net paths hand dragonball an iface_id taken
from the virt interface name, but the vhost-user-net endpoint left
dev_id unassigned, so the device carried no name of its own and was
identified by its socket path inside the hypervisor. Assign dev_id from
the endpoint's interface name so every network backend is identified
the same way by a name the runtime knows.

Also construct dragonball's vhost-user config with struct update syntax
so this commit builds both before and after dragonball's config gains
an iface_id field; the follow-up commit passes dev_id through
explicitly once that field exists.

Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>

src/runtime-rs/crates/hypervisor/src/dragonball/inner_device.rs

@@ -359,6 +359,7 @@ impl DragonballInner {
             queue_size: Some(config.queue_size as u16),
             backend: dragonball::api::v1::Backend::VhostUser(DragonballVhostUserConfig {
                 sock_path: config.socket_path.clone(),
+                ..Default::default()
             }),
             guest_mac,
             use_shared_irq: None,

src/runtime-rs/crates/resource/src/network/endpoint/vhost_user_endpoint.rs

@@ -58,6 +58,10 @@ impl VhostUserEndpoint {
 
     fn get_network_config(&self) -> VhostUserConfig {
         VhostUserConfig {
+            // Name the device after the virt interface, as the virtio-net and
+            // vhost-net paths do, so the hypervisor identifies it by a name
+            // the runtime knows rather than by its socket path.
+            dev_id: self.name.clone(),
             socket_path: self.socket_path.clone(),
             mac_address: self.guest_mac.clone(),
             device_type: VhostUserType::Net,