feat(etcd): add upgrade example OpsRequest (#2542)

(cherry picked from commit 345906c)

Author: weicao

examples/etcd/upgrade.yaml

@@ -0,0 +1,14 @@
+apiVersion: operations.kubeblocks.io/v1alpha1
+kind: OpsRequest
+metadata:
+  name: etcd-upgrade
+  namespace: demo
+spec:
+  # Specifies the name of the Cluster resource that this operation is targeting.
+  clusterName: etcd-cluster
+  type: Upgrade
+  upgrade:
+    components:
+    - componentName: etcd
+      # Valid options are: [3.6.1,3.5.15,3.5.6]
+      serviceVersion: "3.6.1"