feature: support secret reference for Redis password in MCP Server (#3006)

Co-authored-by: 澄潭 <zty98751@alibaba-inc.com>

test/e2e/conformance/tests/configmap-mcp-redis-secret.yaml

@@ -0,0 +1,41 @@
+# Copyright (c) 2025 Alibaba Group Holding Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+apiVersion: v1
+kind: Secret
+metadata:
+  name: redis-credentials
+  namespace: higress-system
+type: Opaque
+stringData:
+  password: InitialSecretFromSecret123
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: higress-conformance-infra-configmap-mcp-redis-secret-test
+  namespace: higress-conformance-infra
+spec:
+  ingressClassName: higress
+  rules:
+    - host: "mcp-redis-secret.example.com"
+      http:
+        paths:
+          - pathType: Prefix
+            path: "/mcp"
+            backend:
+              service:
+                name: infra-backend-v3
+                port:
+                  number: 8080