api: convert Window to dyn Window

This should allow us to make future split of backends much easier.
The `Box<dyn Window>` is a _temporary_ solution, which will be
removed with the future updates when we decide on how the Window
should be stored.

src/platform_impl/windows/monitor.rs

@@ -16,7 +16,6 @@ use crate::dpi::{PhysicalPosition, PhysicalSize};
 use crate::monitor::VideoModeHandle as RootVideoModeHandle;
 use crate::platform_impl::platform::dpi::{dpi_to_scale_factor, get_monitor_dpi};
 use crate::platform_impl::platform::util::has_flag;
-use crate::platform_impl::platform::window::Window;
 
 #[derive(Clone)]
 pub struct VideoModeHandle {
@@ -136,17 +135,6 @@ pub fn current_monitor(hwnd: HWND) -> MonitorHandle {
     MonitorHandle::new(hmonitor)
 }
 
-impl Window {
-    pub fn available_monitors(&self) -> VecDeque<MonitorHandle> {
-        available_monitors()
-    }
-
-    pub fn primary_monitor(&self) -> Option<MonitorHandle> {
-        let monitor = primary_monitor();
-        Some(monitor)
-    }
-}
-
 pub(crate) fn get_monitor_info(hmonitor: HMONITOR) -> Result<MONITORINFOEXW, io::Error> {
     let mut monitor_info: MONITORINFOEXW = unsafe { mem::zeroed() };
     monitor_info.monitorInfo.cbSize = mem::size_of::<MONITORINFOEXW>() as u32;