[DOC] Document cloud/cluster engine recommendations for cudf-polars

We have benchmark evidence pointing to configuration choices for cloud deployments, for example pinned memory defaults, but none of that guidance is written down anywhere. We should document recommended engine and configuration choices for running cudf-polars on cloud infrastructure, including benchmarks.

Start by finding the benchmark evidence referenced in the issue and the existing cudf-polars cloud documentation entry point. Compare the reported engine and configuration choices, including pinned-memory defaults, across the documented cloud setups. Done means the recommendations and supporting benchmarks are written down in the appropriate documentation location.

Written by the indexing model from the issue text.