Scene loading gets stuck

[leanmendoza]

This is without the working progress of #416
But I think the issue is mainly in not allowing the scene to run without the loading GLTFs being finished and because there is no timeout, the loading state is forever on LOADING, so maybe the next can help:

• Add timeout to resource loading (this would avoid the sticking)
• Show how many resources are loading as debug (copy of how Bevy-explorer is doing) and allow to copy the list with a button visible when the message A little Longer than expected is showed