docs(kubernetes): add more fleshed-out example of a Demo Kubernetes cluster (#2329)

This Kubernetes cluster has:

- vLLM for serving an inference model
- vLLM for serving a safety model
- Postgres DB (for metadata and other state for the Llama Stack distro)
- Chroma DB for Vector IO (memory)

Perhaps most importantly, this was me trying to learn Kubernetes for the
first time.

## Test Plan

Run `sh apply.sh` against an EKS cluster, then after `kubectl
port-forward service/llama-stack-service 8321:8321` and after many
attempts, we have finally:

<img width="1589" alt="image"
src="https://github.com/user-attachments/assets/c69f242d-6aaa-4def-9f7c-172113b8bfc1"
/>

<img width="1978" alt="image"
src="https://github.com/user-attachments/assets/cf678404-f551-4fa5-9077-bebe3e8e8ae8"
/>

docs/source/distributions/k8s/stack-k8s.yaml.template

@@ -0,0 +1,80 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: llama-pvc
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: llama-stack-server
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: llama-stack
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: llama-stack
+    spec:
+      containers:
+      - name: llama-stack
+        image: llamastack/distribution-remote-vllm:latest
+        imagePullPolicy: Always # since we have specified latest instead of a version
+        env:
+        - name: ENABLE_CHROMADB
+          value: "true"
+        - name: CHROMADB_URL
+          value: http://chromadb.default.svc.cluster.local:6000
+        - name: VLLM_URL
+          value: http://vllm-server.default.svc.cluster.local:8000/v1
+        - name: VLLM_MAX_TOKENS
+          value: "3072"
+        - name: VLLM_SAFETY_URL
+          value: http://vllm-server-safety.default.svc.cluster.local:8001/v1
+        - name: POSTGRES_HOST
+          value: postgres-server.default.svc.cluster.local
+        - name: POSTGRES_PORT
+          value: "5432"
+        - name: VLLM_TLS_VERIFY
+          value: "false"
+        - name: INFERENCE_MODEL
+          value: "${INFERENCE_MODEL}"
+        - name: SAFETY_MODEL
+          value: "${SAFETY_MODEL}"
+        - name: TAVILY_SEARCH_API_KEY
+          value: "${TAVILY_SEARCH_API_KEY}"
+        command: ["python", "-m", "llama_stack.distribution.server.server", "--config", "/etc/config/stack_run_config.yaml", "--port", "8321"]
+        ports:
+          - containerPort: 8321
+        volumeMounts:
+          - name: llama-storage
+            mountPath: /root/.llama
+          - name: llama-config
+            mountPath: /etc/config
+      volumes:
+      - name: llama-storage
+        persistentVolumeClaim:
+          claimName: llama-pvc
+      - name: llama-config
+        configMap:
+          name: llama-stack-config
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: llama-stack-service
+spec:
+  selector:
+    app.kubernetes.io/name: llama-stack
+  ports:
+  - protocol: TCP
+    port: 8321
+    targetPort: 8321
+  type: ClusterIP