Allow users to subscribe to identity_connected, identity_disconnected and CLI SQL events

[jdetter]

We currently don't support allowing clients to subscribe to the connect/disconnect reducers and we also don't support allowing clients to subscribe to arbitrary CLI SQL events (like running spacetime sql <module> "INSERT INTO <table-name> <values>"). We should implement callbacks for these events.

We started suppressing these errors in this PR: clockworklabs/SpacetimeDB#1461

See implementation notes pointed out by Phoebe: https://github.com/orgs/clockworklabs/projects/22/views/16?filterQuery=priority%3AP1+builtin&pane=issue&itemId=67001837