x11: Implement various window functions (#12070)

This (mostly) allows the CSD added in
https://github.com/zed-industries/zed/pull/11525 to work in X11. It's
still a bit buggy as it detects a second window drag right after the
first one finishes, but it's probably better to change the way window
drags are detected in the title bar itself (as that causes other
issues).

The CSD can be tested by changing the return value of
`should_render_window_controls` to true.

Also fixes F11 crashing.

Release Notes:

- N/A

crates/gpui/src/window.rs

@@ -1147,12 +1147,12 @@ impl<'a> WindowContext<'a> {
         self.window.platform_window.zoom();
     }
 
-    /// Opens the native title bar context menu, useful when implementing client side decorations (Wayland only)
+    /// Opens the native title bar context menu, useful when implementing client side decorations (Wayland and X11)
     pub fn show_window_menu(&self, position: Point<Pixels>) {
         self.window.platform_window.show_window_menu(position)
     }
 
-    /// Tells the compositor to take control of window movement (Wayland only)
+    /// Tells the compositor to take control of window movement (Wayland and X11)
     ///
     /// Events may not be received during a move operation.
     pub fn start_system_move(&self) {