Hide the mouse when the user is typing in the editor - take 2 (#27519)

Closes #4461

Take 2 on https://github.com/zed-industries/zed/pull/25040. 

Fixes panic caused due to using `setHiddenUntilMouseMoves` return type
to `set` cursor on macOS.

Release Notes:

- Now cursor hides when the user is typing in editor. It will stay
hidden until it is moved again. This behavior is `true` by default, and
can be configured with `hide_mouse_while_typing` in settings.

---------

Co-authored-by: Peter Tripp <peter@zed.dev>
Co-authored-by: Thomas Mickley-Doyle <thomas@zed.dev>
Co-authored-by: Agus <agus@zed.dev>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Agus Zubiaga <hi@aguz.me>
Co-authored-by: Angelk90 <angelo.k90@hotmail.it>

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

@@ -891,6 +891,11 @@ impl Platform for MacPlatform {
     /// in macOS's [NSCursor](https://developer.apple.com/documentation/appkit/nscursor).
     fn set_cursor_style(&self, style: CursorStyle) {
         unsafe {
+            if style == CursorStyle::None {
+                let _: () = msg_send![class!(NSCursor), setHiddenUntilMouseMoves:YES];
+                return;
+            }
+
             let new_cursor: id = match style {
                 CursorStyle::Arrow => msg_send![class!(NSCursor), arrowCursor],
                 CursorStyle::IBeam => msg_send![class!(NSCursor), IBeamCursor],
@@ -925,6 +930,7 @@ impl Platform for MacPlatform {
                 CursorStyle::DragLink => msg_send![class!(NSCursor), dragLinkCursor],
                 CursorStyle::DragCopy => msg_send![class!(NSCursor), dragCopyCursor],
                 CursorStyle::ContextualMenu => msg_send![class!(NSCursor), contextualMenuCursor],
+                CursorStyle::None => unreachable!(),
             };
 
             let old_cursor: id = msg_send![class!(NSCursor), currentCursor];