Make a macro for less boilerplate when moving variables (#12182)

Also: 
- Simplify open listener implementation
- Add set_global API to global traits

Release Notes:

- N/A

crates/zed/src/zed.rs

@@ -11,7 +11,7 @@ use collections::VecDeque;
 use editor::{scroll::Autoscroll, Editor, MultiBuffer};
 use gpui::{
     actions, point, px, AppContext, AsyncAppContext, Context, FocusableView, MenuItem, PromptLevel,
-    TitlebarOptions, View, ViewContext, VisualContext, WindowKind, WindowOptions,
+    ReadGlobal, TitlebarOptions, View, ViewContext, VisualContext, WindowKind, WindowOptions,
 };
 pub use open_listener::*;