Fix or promote leftover TODOs and GPUI APIs (#12514)

fixes https://github.com/zed-industries/zed/issues/11966

Release Notes:

- N/A

crates/gpui/src/platform/app_menu.rs

@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use crate::{Action, AppContext, Platform};
 use util::ResultExt;
 
@@ -10,6 +12,16 @@ pub struct Menu<'a> {
     pub items: Vec<MenuItem<'a>>,
 }
 
+impl<'a> Menu<'a> {
+    /// Create an OwnedMenu from this Menu
+    pub fn owned(self) -> OwnedMenu {
+        OwnedMenu {
+            name: self.name.to_string().into(),
+            items: self.items.into_iter().map(|item| item.owned()).collect(),
+        }
+    }
+}
+
 /// The different kinds of items that can be in a menu
 pub enum MenuItem<'a> {
     /// A separator between items
@@ -60,6 +72,73 @@ impl<'a> MenuItem<'a> {
             os_action: Some(os_action),
         }
     }
+
+    /// Create an OwnedMenuItem from this MenuItem
+    pub fn owned(self) -> OwnedMenuItem {
+        match self {
+            MenuItem::Separator => OwnedMenuItem::Separator,
+            MenuItem::Submenu(submenu) => OwnedMenuItem::Submenu(submenu.owned()),
+            MenuItem::Action {
+                name,
+                action,
+                os_action,
+            } => OwnedMenuItem::Action {
+                name: name.into(),
+                action,
+                os_action,
+            },
+        }
+    }
+}
+
+/// A menu of the application, either a main menu or a submenu
+#[derive(Clone)]
+pub struct OwnedMenu {
+    /// The name of the menu
+    pub name: Cow<'static, str>,
+
+    /// The items in the menu
+    pub items: Vec<OwnedMenuItem>,
+}
+
+/// The different kinds of items that can be in a menu
+pub enum OwnedMenuItem {
+    /// A separator between items
+    Separator,
+
+    /// A submenu
+    Submenu(OwnedMenu),
+
+    /// An action that can be performed
+    Action {
+        /// The name of this menu item
+        name: String,
+
+        /// the action to perform when this menu item is selected
+        action: Box<dyn Action>,
+
+        /// The OS Action that corresponds to this action, if any
+        /// See [`OsAction`] for more information
+        os_action: Option<OsAction>,
+    },
+}
+
+impl Clone for OwnedMenuItem {
+    fn clone(&self) -> Self {
+        match self {
+            OwnedMenuItem::Separator => OwnedMenuItem::Separator,
+            OwnedMenuItem::Submenu(submenu) => OwnedMenuItem::Submenu(submenu.clone()),
+            OwnedMenuItem::Action {
+                name,
+                action,
+                os_action,
+            } => OwnedMenuItem::Action {
+                name: name.clone(),
+                action: action.boxed_clone(),
+                os_action: *os_action,
+            },
+        }
+    }
 }
 
 // TODO: As part of the global selections refactor, these should