Provide a way to set cursor area for IME cursor

Rename `Window::set_ime_position` to `Window::set_ime_cursor_area`
adding a way to create cursor exclusive zone.

Fixes #2886.

src/platform_impl/linux/x11/window.rs

@@ -1510,7 +1510,7 @@ impl UnownedWindow {
     }
 
     #[inline]
-    pub fn set_ime_position(&self, spot: Position) {
+    pub fn set_ime_cursor_area(&self, spot: Position, _size: Size) {
         let (x, y) = spot.to_physical::<i32>(self.scale_factor()).into();
         let _ = self
             .ime_sender