Fix ScalableContainer irrepairably altering content size #2339
Also took it a step further and removed one layer of nested containers.
Note: Spinners are now slightly smaller than before because we actually have a 4:3 size container. We'll need to alter this back if we want it to overfill the screen. I've held back on this for now, but let me know if you want me to make this change in this PR.