Figure out whether to create `EventSystem` automatically or not

[UnexomWid]

First, check if Tale actually requires EventSystem. The default choice picker might need it.

There must be only 1 EventSystem object in the scene. However, since the Tale master persists across scenes, Tale can't know ahead of time if it should create the object, because another EventSystem might be part of a future scene.

The only solution I see for the moment is to create such an object anyways, and dynamically disable it during scenes that have their own EventSystem.