[Core cleanup] Rename core to event

[aniav]

This dependends on

• [x] #361
• [x] #362
• [x] #363
• [x] #364
• [ ] #365

Core app has grown a lot in the past months. We should move things not related to Event to other apps. When this is done we can rename the core app to event. We should also decide what to do with helpers/utils used in multiple apps. Let's discuss this topic here before implementing.

I would propose doing a list of things used in multiple apps and decide for each of them, maybe something is used across apps but it actually belongs to one of them? Maybe we should introduce utils app of some kind (which I am not a fan of because it ends up gathering various things and creating a lot of clutter)?

[ramonsaraiva]

Can you mark #362 as done?

[ramonsaraiva]

I can potentially tackle #365

[amreshk005]

@aniav can I work this.