Adds notes explaining that Ray's support on Azure, Aliyun, and SLURM is community-maintained.
Rephrases the mention of K8s support in the intro.
This PR replaces https://github.com/ray-project/ray/pull/25504.
Using Ray on SLURM system is documented but missing some pitfalls about network. This PR adds some information about port binding and address binding (I will open a feature request with more and link it here later).
I did not put any real recommendation on this last point since `--address` did not work. I had cannot resolve issue after setting an internal IP although it's reachable.
