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/ingress-k8s.yaml.template

@@ -0,0 +1,12 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: llama-stack-service
+spec:
+  type: LoadBalancer
+  selector:
+    app.kubernetes.io/name: llama-stack
+  ports:
+    - port: 8321
+      targetPort: 8321
+      protocol: TCP