docs: add AWS (EC2/SageMaker) deployment + benchmarking guide

Docs: add an AWS deployment + benchmarking guide for TGI. - Adds a tutorial page covering EC2 (Docker) and SageMaker real-time endpoints. - Includes a practical benchmarking section (what to measure + a warmup/load-test workflow). - Links the new page from the docs toctree. Docs-only change.