vmm: Report enabled features from the '/vmm.ping' endpoint

Fixes: #5817

Signed-off-by: Bo Chen <chen.bo@intel.com>

vmm/src/api/mod.rs

@@ -171,6 +171,7 @@ pub struct VmmPingResponse {
     pub build_version: String,
     pub version: String,
     pub pid: i64,
+    pub features: Vec<String>,
 }
 
 #[derive(Clone, Deserialize, Serialize, Default, Debug)]

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

@@ -445,6 +445,10 @@ components:
         pid:
           type: integer
           format: int64
+        features:
+          type: array
+          items:
+            type: string
       description: Virtual Machine Monitor information
 
     VmInfo: