virtio-balloon: Add memory_actual_size to vm.info to show memory actual size

The virtio-balloon change the memory size is asynchronous.
VirtioBalloonConfig.actual of balloon device show current balloon size.

This commit add memory_actual_size to vm.info to show memory actual size.

Signed-off-by: Hui Zhu <teawater@antfin.com>

vmm/src/api/mod.rs

@@ -145,6 +145,7 @@ pub type ApiResult<T> = std::result::Result<T, ApiError>;
 pub struct VmInfo {
     pub config: Arc<Mutex<VmConfig>>,
     pub state: VmState,
+    pub memory_actual_size: u64,
 }
 
 #[derive(Clone, Deserialize, Serialize)]

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -360,6 +360,9 @@ components:
         state:
           type: string
           enum: [Created, Running, Shutdown, Paused]
+        memory_actual_size:
+          type: integer
+          format: int64
       description: Virtual Machine information
 
     VmCounters: