envoy-gateway: add seerr-test.jsme.be listener + cert (OIDC preview test)

Temporary listener/cert for the seerr-test instance running the
preview-new-oidc build. Remove along with the seerr-test workload when
testing is done.

envoy-gateway/seerr/test-gateway-patch.yaml

@@ -0,0 +1,19 @@
+- op: add
+  path: /spec/listeners/-
+  value:
+    name: seerr-test
+    protocol: HTTPS
+    port: 443
+    hostname: "seerr-test.jsme.be"
+    allowedRoutes:
+      namespaces:
+        from: Selector
+        selector:
+          matchLabels:
+            kubernetes.io/metadata.name: seerr
+    tls:
+      mode: Terminate
+      certificateRefs:
+        - kind: Secret
+          name: seerr-test-tls
+          namespace: envoy-gateway