Native Wayland support through wlr-layer-shell

[pixelomer]

Relevant issue: #43

The Wayland implementation is mostly done, but supporting both Qt widgets and Wayland as different modes required some changes in the program's design which may have broken certain things. These need to be fixed and verified before this feature can be added to the main branch.

• Split backends for:
  • wlr-layer-shell
  • Qt widgets
  • Windowed mode
• Base wlr-layer-shell implementation
• Ensure all existing backends (Qt widgets and windowed mode) continue working normally on all platforms and desktop environments
• Maintain multi-monitor support
• Maintain cross-platform compatibility (Wayland code should be isolated to Linux)
• Option to switch between all backends without restart
• Verify Wayland functionality on commonly used desktop environments (mainly KDE Plasma, Hyprland and other wlroots compositors)