Several global limits added in 2023-2025 are missing from doc guides

[michaelklishin]

Describe the bug

A number of global (per cluster) limits introduced in 2023-2025 do not have an obvious place to put them:

1. For virtual hosts: Introduce a limit for how many virtual hosts can be created in a cluster rabbitmq-server#7798
2. For queues and streams Introduce a limit for how many virtual hosts can be created in a cluster rabbitmq-server#7798
3. For exchanges Add a configurable limit for number of exchanges rabbitmq-server#14304

We do have per virtual host limits documented because there is a natural place for those docs to go: the virtual hosts guide.

Expected behavior

Those limits should be documented. Protecting clusters from application-induced resource leaks is a thing.