linux/x11: Restore differentiation of mouse/keyboard focus (#13995)

This restores https://github.com/zed-industries/zed/pull/13943 which was
reverted in #13974 because it was possible to get in a state where focus
could not be restored on a window.

In this PR there's an additional change: `FocusIn` and `FocusOut` events
are always handled, even if the `event.mode` is not "NORMAL". In my
testing, `alt-tabbing` between windows didn't produce `FocusIn` and
`FocusOut` events when we had that check. Now, with the check removed,
it's possible to switch focus between two windows again with `alt-tab`.


Release Notes:

- N/A

---------

Co-authored-by: Conrad <conrad@zed.dev>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/gpui/src/platform/mac/window.rs

@@ -940,6 +940,11 @@ impl PlatformWindow for MacWindow {
         unsafe { self.0.lock().native_window.isKeyWindow() == YES }
     }
 
+    // is_hovered is unused on macOS. See WindowContext::is_window_hovered.
+    fn is_hovered(&self) -> bool {
+        false
+    }
+
     fn set_title(&mut self, title: &str) {
         unsafe {
             let app = NSApplication::sharedApplication(nil);
@@ -1061,6 +1066,8 @@ impl PlatformWindow for MacWindow {
         self.0.as_ref().lock().activate_callback = Some(callback);
     }
 
+    fn on_hover_status_change(&self, _: Box<dyn FnMut(bool)>) {}
+
     fn on_resize(&self, callback: Box<dyn FnMut(Size<Pixels>, f32)>) {
         self.0.as_ref().lock().resize_callback = Some(callback);
     }