Plugin Dependencies

[cart]

Some plugins require other plugins to work. We should allow plugins to define dependencies that must be registered before them. This would also help ensure that plugins are registered in the correct order (where that matters).

[alice-i-cecile]

Plugin ordering could be solved by #1255 instead.

[hukasu]

My proposition is:
Plugin only has one method setup which has aSettingUpApp as argument and which only has add_systems and configure_sets (my use of app is not that thorough so the only methods that I would use are these), they don't take a schedule as an argument as it is implicit that it is the "Build" schedule

struct MyPlugin;
impl Plugin for MyPlugin {
  fn setup(app: &mut SettingUpApp) {
    #[cfg(feature = "wasm32"]
    app.configure_sets((MyPluginSet::Systems, MyPluginSet::WasmResource).chain());

 
   app.add_systems(insert_systems.in_set(MyPluginSet::Systems));
    #[cfg(feature = "wasm32")]
    app.add_systems(wasm_resources.in_set(MyPluginSet::WasmResource));
  }
}

Or something like this