add TOC and renaming:x

Author: matternst7258

articles/operator-nexus/TOC.yml

@@ -13,8 +13,15 @@
       href: concepts-compute.md
     - name: Storage overview
       href: concepts-storage.md
-    - name: Cluster deployment
-      href: concepts-cluster-deployment-overview.md
+    - name: Cluster deployment and upgrades
+      expanded: false
+      items:
+        - name: Cluster deployment
+          href: concepts-cluster-deployment-overview.md
+        - name: Cluster Runtime upgrade
+          href: concepts-cluster-upgrade-overview.md
+        - name: Cluster management upgrade
+          href: concepts-cluster-management-upgrade.md
     - name: Network Fabric
       expanded: false
       items: