Fixed-list clients

[UkoeHB]

Many games have a predefined client list. In that case you can assign client ids as indices into the client list, and access clients on the server in O(1) instead of O(n) or O(logn).

This is relevant for client visibility, because to set the visibility of an entity on a client you need to access that client in the client list. Setting visibility can be considered the hot path, since you may need to update visibility frequently for many entities.

Options:

• Server plugin config to enable a fixed-list client optimization.
• Feature-level compile flag to avoid branching + server plugin config to set the number of clients.

Note that this would require changes to how connection status is tracked.