[Doc] Clarification of documentation regarding multi-tenancy

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### What issue do you find in Pulsar docs?

In the [multi tenancy section of the docs](https://pulsar.apache.org/docs/2.11.x/concepts-multi-tenancy/) it says "They [tenants] are also the administrative unit at which storage quotas, message TTL, and isolation policies can be managed.".

After I read this I expected to see commands on the admin CLI for configuring these things for a particular tenant, but I only found commands for single namespaces.

For example `set-message-ttl`, `set-backlog-quota`, `set-persistence` are all namespace level configuration.

Is there some method of configuring tenant wide policies, or am I just interpreting the documentation wrong?

Thanks!

### What is your suggestion?

I don't currently have one. I am asking a question.

### Any reference?

https://pulsar.apache.org/docs/2.11.x/concepts-multi-tenancy/

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Start with the linked multi-tenancy documentation and compare its statement about storage quotas, message TTL, and isolation policies with the admin CLI commands named in the issue: set-message-ttl, set-backlog-quota, and set-persistence. Confirm whether tenant-wide configuration exists, then clarify the documentation so its scope and supported commands are unambiguous.

Written by the indexing model from the issue text.