Switch back from custom benchmarks to Bevy's in-tree benchmarks

[BD103]

I don't have the time nor energy to write and maintain my own set of benchmarks. In this light, we should switch back to using Bevy's benches.

I would like to keep the file size benchmarks, but the rest can go. This will probably require creating a new Bencher project, since I don't want to completely remove the old one.