chore: remove platform WindowId's

WindowId is a window _identifier_, and as such doesn't store anything
(unlike a _handle_). So we can safely make only be defined once, in the
core crate.

There are a few backends where we still use `into_raw` internally; I
consider these patterns discouraged, we should not be passing around
important state in the window id.

src/platform_impl/linux/mod.rs

@@ -107,19 +107,6 @@ impl Default for PlatformSpecificWindowAttributes {
 pub(crate) static X11_BACKEND: Lazy<Mutex<Result<Arc<XConnection>, XNotSupported>>> =
     Lazy::new(|| Mutex::new(XConnection::new(Some(x_error_callback)).map(Arc::new)));
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct WindowId(u64);
-
-impl WindowId {
-    pub const fn into_raw(self) -> u64 {
-        self.0
-    }
-
-    pub const fn from_raw(id: u64) -> Self {
-        Self(id)
-    }
-}
-
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum DeviceId {
     #[cfg(x11_platform)]