Document factors that contribute to user server start time about docs HOT 1 OPEN

I believe we should prioritize this issue, so I will add it to the sprint board and increase its priority.

Documenting what contributes to node startup times is especially important now that we are transitioning to have bigger nodes be shared by multiple users. It's important to document that each user that will generate a new node event, will see a longer wait time than the other users that will fit onto an existing node.

Also, in the context of an event, such a setup enables the instructor to "pre-warm" the hub by themselves, by just starting a server before the event. That server star event, will spin up a node and that node will be ready for the initial hub users to use.

from docs.