tests: Add direct kernel boot test for confidential VMs

Add test_direct_kernel_boot to the common_cvm integration test
module to verify that boot, CPU, memory, and MSI interrupt
functionality work correctly in confidential guest environments.

The test creates an Ubuntu Jammy-based confidential VM using
GuestFactory and delegates to the existing
_test_direct_kernel_boot helper.

Signed-off-by: Muminul Islam <muislam@microsoft.com>

cloud-hypervisor/tests/integration.rs

@@ -15018,4 +15018,12 @@ mod common_cvm {
             GuestFactory::new_confidential_guest_factory().create_guest(Box::new(disk_config));
         _test_pci_multiple_segments(&guest, num_pci_segments, 5);
     }
+
+    #[test]
+    fn test_direct_kernel_boot() {
+        let disk_config = UbuntuDiskConfig::new(JAMMY_IMAGE_NAME.to_string());
+        let guest =
+            GuestFactory::new_confidential_guest_factory().create_guest(Box::new(disk_config));
+        _test_direct_kernel_boot(&guest);
+    }
 }