AsyncSceneInheritOutline to use SceneInstanceReady / be reversible

[komadori]

This attempts to address:

• @Shatur's request in Add AsyncSceneOutline #30 that that AsyncSceneInheritOutline should use the SceneInstanceReady event
• @rparrett's request in AsyncSceneInheritOutline doesn't propagate outline component removal. #34 that removing AsyncScenenInheritOutline should reverse its effect (and by implication that it can be added after the scene has loaded).

[Shatur]

Why do you need both systems? Isn't SceneInstanceReady emitted every time after an instance spawn?

[komadori]

This supports the use case that you first spawn a scene, the scene becomes ready, and then only later add the outlining components to it.

Personally, I always add the outline components at spawning time and never remove them, but I can't say that an approach where you add and remove the components is wrong. I don't know how efficient the Added query filter is though, so perhaps this is no better than not using the event.

[Shatur]

Makes sense.

Regardless complexity see this.