Better handling of high latency

[ScottPeterJohnson]

• [x] Add a testing parameter to add delay between events being received
• [ ] Add a few helpful builtins for e.g. disabling a button until its callback has been processed
• [ ] Possibly something similar to Kweb's immediate mode callbacks?

[ScottPeterJohnson]

Added testing delay parameter, and also consistent mapping of callbacks under a component to the same callback ID, so long as they share the same render position (DOM tree + event name). This should help translate events that are lost between updates at high latency.