Bevy 0.16 updates

Assorted updates for 0.16 compatibility. There's only two more TODOs: * I want to transition `rotating-column` to use animation clips rather than a 3rd party crate, which will help make it easier to keep up to date with future releases and demo core APIS. * `dissolve-sphere-standard-material-extension` currently has an issue where the shadow doesn't have the dissolved gaps applied. This worked in 0.15 when discarding in the fragment prepass so I have to spend a bit of time to git bisect and figure out when this stopped working on bevy main. Additionally I want to continue to add more structure to the repo after this PR, introducing some folders for categorization as the number of examples grows. Each example should show a concrete game feature or apply a Bevy API in a specific way to achieve an end result.