Upgrade to Bevy 0.12

[CleanCut]

I started upgrading the underlying version of Bevy from 0.8 a couple months ago and got distracted. Today I sat down and spent a few hours upgrading all the way to Bevy 0.12.

Breaking changes

• WindowDescriptor has been renamed to Window
• You must new add #[derive(Resource)] above your GameState struct.
• It is no longer possible to use the unit type () instead of a GameState struct. Always create a GameState struct (it can be an empty struct with no fields).
• The Timer now takes a TimerMode enum variant instead of a bool. Use TimerMode::Once for a timer that runs once, or TimerMode::Repeating for a repeating timer.
• The following KeyCode variants have been renamed:
  • LShift -> ShiftLeft
  • RShift -> ShiftRight
  • LAlt -> AltLeft
  • RAlt -> AltRight
  • LBracket -> BracketLeft
  • RBracket -> BracketRight
  • LControl -> ControlLeft
  • RControl -> ControlRight
  • LShift -> ShiftLeft
  • LWin -> SuperLeft
  • RWin -> SuperRight

Improved

• Update bevy from 0.8 to 0.12
• Update bevy_prototype_lyon from 0.6 to 0.10
• Update ron from 0.7 to 0.8
• Fixed some inconsistent parameter names in examples
• Some examples' audio was turned down lower