- Remove all references to impl from api and lib packages; all internal
interaction with impl now goes through InternalFlywheelApi
- Separate and organize backend and impl mixins and extensions
- Remove camera position component getters from VisualFrameContext
- Improve accuracy of fog data update detection
- Make PoseTransformStack.stack private and add unwrap method
- Rename BackendManager.isOn -> isBackendOn (and associated methods in
other classes)
