feat: open benchmark template and doc (#1465)

## What does this PR do?
- Provide a distro template to let developer easily run the open
benchmarks llama stack supports on llama and non-llama models.
- Provide doc on how to run open benchmark eval via CLI and open
benchmark contributing guide

[//]: # (If resolving an issue, uncomment and update the line below)
(Closes #1375 )

## Test Plan
open benchmark eval results on llama, gpt, gemini and clause
<img width="771" alt="Screenshot 2025-03-06 at 7 33 05 PM"
src="https://github.com/user-attachments/assets/1bd85456-b9b9-4b37-af76-4ce1d2bac00e"
/>

doc preview
<img width="944" alt="Screenshot 2025-03-06 at 7 33 58 PM"
src="https://github.com/user-attachments/assets/f4e5866d-b395-4c40-aa8b-080edeb5cdb6"
/>
<img width="955" alt="Screenshot 2025-03-06 at 7 34 04 PM"
src="https://github.com/user-attachments/assets/629defb6-d5e4-473c-aa03-308bce386fb4"
/>

<img width="965" alt="Screenshot 2025-03-06 at 7 35 29 PM"
src="https://github.com/user-attachments/assets/c21ff96c-9e8c-4c54-b6b8-25883125f4cf"
/>

<img width="957" alt="Screenshot 2025-03-06 at 7 35 37 PM"
src="https://github.com/user-attachments/assets/47571c90-1381-4e2c-bbed-c4f3a60578d0"
/>

distributions/dependencies.json

@@ -453,6 +453,42 @@
     "transformers",
     "uvicorn"
   ],
+  "open_benchmark": [
+    "aiosqlite",
+    "autoevals",
+    "blobfile",
+    "chardet",
+    "chromadb-client",
+    "datasets",
+    "fastapi",
+    "fire",
+    "httpx",
+    "litellm",
+    "matplotlib",
+    "mcp",
+    "nltk",
+    "numpy",
+    "openai",
+    "opentelemetry-exporter-otlp-proto-http",
+    "opentelemetry-sdk",
+    "pandas",
+    "pillow",
+    "psycopg2-binary",
+    "pymongo",
+    "pypdf",
+    "redis",
+    "requests",
+    "scikit-learn",
+    "scipy",
+    "sentencepiece",
+    "sqlite-vec",
+    "together",
+    "tqdm",
+    "transformers",
+    "uvicorn",
+    "sentence-transformers --no-deps",
+    "torch torchvision --index-url https://download.pytorch.org/whl/cpu"
+  ],
   "remote-vllm": [
     "aiosqlite",
     "autoevals",