Cleaning Up Xcode Simulator Runtimes

I have a MacBook Air M3 with 256GB of storage. It is not a lot. I use it for my Python projects and iOS projects, so Xcode and all its baggage are a permanent fixture. Recently I noticed my disk was almost full, and my System Data was over 100GB. I had no idea what was in there or how to clean it. I tried the usual — clearing caches, emptying the bin — and nothing moved the needle.