Reduce serialized object size

We should aim to make our serialized objects as small as possible, or partition them into smaller data pieces we combine together piece-by-piece so that they can be loaded one piece at a time over time. This can be tricky to manage for Prefabs since Unity does not inherently support nested Prefabs, and so we would be implementing such a system ourselves, which is a notoriously difficult problem to solve in Unity. UI Prefabs are good candidates for separating into smaller pieces, since we don't normally need the entire UI at any given moment, and so we can usually afford to load them in one piece at a time.