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-configmap.yaml

@@ -0,0 +1,128 @@
+apiVersion: v1
+data:
+  stack_run_config.yaml: |
+    version: '2'
+    image_name: kubernetes-demo
+    apis:
+    - agents
+    - inference
+    - safety
+    - telemetry
+    - tool_runtime
+    - vector_io
+    providers:
+      inference:
+      - provider_id: vllm-inference
+        provider_type: remote::vllm
+        config:
+          url: ${env.VLLM_URL:http://localhost:8000/v1}
+          max_tokens: ${env.VLLM_MAX_TOKENS:4096}
+          api_token: ${env.VLLM_API_TOKEN:fake}
+          tls_verify: ${env.VLLM_TLS_VERIFY:true}
+      - provider_id: vllm-safety
+        provider_type: remote::vllm
+        config:
+          url: ${env.VLLM_SAFETY_URL:http://localhost:8000/v1}
+          max_tokens: ${env.VLLM_MAX_TOKENS:4096}
+          api_token: ${env.VLLM_API_TOKEN:fake}
+          tls_verify: ${env.VLLM_TLS_VERIFY:true}
+      - provider_id: sentence-transformers
+        provider_type: inline::sentence-transformers
+        config: {}
+      vector_io:
+      - provider_id: ${env.ENABLE_CHROMADB+chromadb}
+        provider_type: remote::chromadb
+        config:
+          url: ${env.CHROMADB_URL:}
+      safety:
+      - provider_id: llama-guard
+        provider_type: inline::llama-guard
+        config:
+          excluded_categories: []
+      agents:
+      - provider_id: meta-reference
+        provider_type: inline::meta-reference
+        config:
+          persistence_store:
+            type: postgres
+            host: ${env.POSTGRES_HOST:localhost}
+            port: ${env.POSTGRES_PORT:5432}
+            db: ${env.POSTGRES_DB:llamastack}
+            user: ${env.POSTGRES_USER:llamastack}
+            password: ${env.POSTGRES_PASSWORD:llamastack}
+          responses_store:
+            type: postgres
+            host: ${env.POSTGRES_HOST:localhost}
+            port: ${env.POSTGRES_PORT:5432}
+            db: ${env.POSTGRES_DB:llamastack}
+            user: ${env.POSTGRES_USER:llamastack}
+            password: ${env.POSTGRES_PASSWORD:llamastack}
+      telemetry:
+      - provider_id: meta-reference
+        provider_type: inline::meta-reference
+        config:
+          service_name: ${env.OTEL_SERVICE_NAME:}
+          sinks: ${env.TELEMETRY_SINKS:console}
+      tool_runtime:
+      - provider_id: brave-search
+        provider_type: remote::brave-search
+        config:
+          api_key: ${env.BRAVE_SEARCH_API_KEY:}
+          max_results: 3
+      - provider_id: tavily-search
+        provider_type: remote::tavily-search
+        config:
+          api_key: ${env.TAVILY_SEARCH_API_KEY:}
+          max_results: 3
+      - provider_id: rag-runtime
+        provider_type: inline::rag-runtime
+        config: {}
+      - provider_id: model-context-protocol
+        provider_type: remote::model-context-protocol
+        config: {}
+    metadata_store:
+      type: postgres
+      host: ${env.POSTGRES_HOST:localhost}
+      port: ${env.POSTGRES_PORT:5432}
+      db: ${env.POSTGRES_DB:llamastack}
+      user: ${env.POSTGRES_USER:llamastack}
+      password: ${env.POSTGRES_PASSWORD:llamastack}
+      table_name: llamastack_kvstore
+    inference_store:
+      type: postgres
+      host: ${env.POSTGRES_HOST:localhost}
+      port: ${env.POSTGRES_PORT:5432}
+      db: ${env.POSTGRES_DB:llamastack}
+      user: ${env.POSTGRES_USER:llamastack}
+      password: ${env.POSTGRES_PASSWORD:llamastack}
+    models:
+    - metadata:
+        embedding_dimension: 384
+      model_id: all-MiniLM-L6-v2
+      provider_id: sentence-transformers
+      model_type: embedding
+    - metadata: {}
+      model_id: ${env.INFERENCE_MODEL}
+      provider_id: vllm-inference
+      model_type: llm
+    - metadata: {}
+      model_id: ${env.SAFETY_MODEL:meta-llama/Llama-Guard-3-1B}
+      provider_id: vllm-safety
+      model_type: llm
+    shields:
+    - shield_id: ${env.SAFETY_MODEL:meta-llama/Llama-Guard-3-1B}
+    vector_dbs: []
+    datasets: []
+    scoring_fns: []
+    benchmarks: []
+    tool_groups:
+    - toolgroup_id: builtin::websearch
+      provider_id: tavily-search
+    - toolgroup_id: builtin::rag
+      provider_id: rag-runtime
+    server:
+      port: 8321
+kind: ConfigMap
+metadata:
+  creationTimestamp: null
+  name: llama-stack-config