On Windows and macOS, add API to enable/disable window controls (#2537)

* On Windows and macOS, add API to enable/disable window controls

* fix build

* missing import

* use `WindowButtons` flags

* rename to `[set_]enabled_buttons`

* add example, fix windows impl for minimize

* macOS: Fix button enabling close/minimize while disabling maximized

* Update src/platform_impl/windows/window.rs

Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

* compose the flags on a sep line, use `bool::then`

Co-authored-by: Mads Marquart <mads@marquart.dk>
Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

src/platform_impl/linux/x11/window.rs

@@ -21,7 +21,8 @@ use crate::{
         PlatformSpecificWindowBuilderAttributes, VideoMode as PlatformVideoMode,
     },
     window::{
-        CursorGrabMode, CursorIcon, Icon, Theme, UserAttentionType, WindowAttributes, WindowLevel,
+        CursorGrabMode, CursorIcon, Icon, Theme, UserAttentionType, WindowAttributes,
+        WindowButtons, WindowLevel,
     },
 };
 
@@ -1280,6 +1281,14 @@ impl UnownedWindow {
         self.shared_state_lock().is_resizable
     }
 
+    #[inline]
+    pub fn set_enabled_buttons(&self, _buttons: WindowButtons) {}
+
+    #[inline]
+    pub fn enabled_buttons(&self) -> WindowButtons {
+        WindowButtons::all()
+    }
+
     #[inline]
     pub fn xlib_display(&self) -> *mut c_void {
         self.xconn.display as _