`Target::target` and `Target::target()` return different entities

[aevyrie]

Bevy version

0.15

What you did

Added a picking observer.

What went wrong

.observe(|trigger: Trigger<Pointer<Click>>| {
            info!(
                "Clicked: picking target:{}, target():{}, observer():{}",
                trigger.target,
                trigger.target(),
                trigger.observer()
            );
        });

This prints out three different entities.

Additional information

Discussion on discord:

https://discord.com/channels/691052431525675048/749335865876021248/1324499473098870896

Consider renaming:

• target: the entity on which the event is fired
• listener/observed: the entity to which the observer is attached (was target)
• observed_by: the entity which holds the observer component (was observer)
  • Can we just hide this entirely, and instead provide remove_observer? The fact that the observer lives on its own entity and is not actually a component on the listener is a confusing implementation detail that I think we should hide from the user.
  • As far as the user is concerned, they have no idea that .observe() spawns a new entity, to them, the API looks like they are attaching something to the "listener" entity.