feat: added borderless fullscreen option with F11 toggle

[daveleone]

Add borderless fullscreen support for VM display windows

This change adds an F11-driven borderless fullscreen mode for VM display windows across Windows and macOS.

What changed

• Windows IDD display

  • Adds Toggle Borderless Fullscreen (F11) to the display window system menu.
  • Handles F11 directly in the IDD display window.
  • Prevents F11 from being forwarded to the guest.
  • Restores the previous window style and placement when toggled off.

• macOS display windows

  • Adds borderless fullscreen support to both:
    • IddDisplayWindow for Windows guests.
    • VzDisplayWindow for macOS guests.
  • Updates the app’s F11 menu action to target the currently active display window, instead of only the main application window.

• Main application windows

  • Retains the existing borderless fullscreen action for the main GUI on Windows and macOS.

User experience

Users can press F11 while a VM display window is active to switch between windowed mode and borderless fullscreen. On Windows, the same action is also available from the IDD display window’s system menu.