`DespawnOnEnter` / `DespawnOnExit` can now trigger during same state transitions

In bevy_state, you can define states and transition between them. For example, this can be used to transition between AppState::Menu and AppState::InGame, and run different logic depending on the state the App is in. In 0.18, it became possible to transition from a state to itself: A 'same state transition'. However, there was a bug that made is so that DespawnOnEnter and DespawnOnExit did not trigger for same state transition when they should have.

In 0.19, this bug is fixed. If your application transitions between states using NextState::set(), your application will trigger DespawnOnEnter and DespawnOnExit, even in same state transitions.

If this is undesired, use NextState::set_if_neq() to transition between states. set_if_neq() does not run any state transition schedules if the target state is the same as the current one.