tests: add test for sealed file secrets

add a test for sealed file secrets.

Signed-off-by: ChengyuZhu6 <chengyu.zhu@intel.com>

tests/integration/kubernetes/runtimeclass_workloads/pod-sealed-secret-as-file.yaml

@@ -0,0 +1,35 @@
+# Copyright (c) 2023 Intel Corporation
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+apiVersion: v1
+kind: Pod
+metadata:
+  name: secret-test-pod-cc
+spec:
+  runtimeClassName: kata
+  containers:
+  - name: busybox
+    image: quay.io/prometheus/busybox:latest
+    imagePullPolicy: Always
+    command:
+    - sh
+    - -c
+    - |
+      unseal_data=$(cat /sealed/secret-value/secret)
+      not_sealed_data=$(cat /sealed/not-sealed-secret-value/secret)
+      echo "PROTECTED_SECRET = $unseal_data"
+      echo "UNPROTECTED_SECRET = $not_sealed_data"
+      sleep 1000
+    volumeMounts:
+        - name: sealed-secret-volume
+          mountPath: "/sealed/secret-value"
+        - name: not-sealed-secret-volume
+          mountPath: "/sealed/not-sealed-secret-value"
+  volumes:
+    - name: sealed-secret-volume
+      secret:
+        secretName: sealed-secret
+    - name: not-sealed-secret-volume
+      secret:
+        secretName: not-sealed-secret