PermissionController should emit more granular events

[FrederikBolding]

The PermissionController currently only emits stateChange which makes listening for permission updates more complicated than it needs to be.

[Gudahtt]

We intended the event selector system to be flexible enough to make it easy to listen to sub-state/derived state changes as well.

Are there use-cases where this is inadequate today? Or are selectors too difficult to use in general? (e.g. even just lack of adequate docs)

[FrederikBolding]

@Gudahtt I will admit, I keep forgetting we have a selector system for events 😄 It seems that it generally doesn't get much use yet.

That being said, even with a selector, it might not provide the granularity/context that a dedicated event would. I created this ticket based on a comment from @jiexi that suggested firing an event for a specific origin: MetaMask/metamask-extension#29887 (comment), but I think we could take it a bit further than that too.