Ensure querying keystrokes or actions is safe

This is achieved by moving `available_actions` into `AsyncAppContext` (where
we know no view/window is on the stack) and `keystrokes_for_action` into `LayoutContext`
where we'll fetch the previous frame's ancestors and notify the current view if those
change after we perform a layout.

crates/workspace/src/dock.rs

@@ -726,7 +726,7 @@ mod tests {
             self.update_workspace(|workspace, cx| Dock::move_dock(workspace, anchor, true, cx));
         }
 
-        pub fn hide_dock(&self) {
+        pub fn hide_dock(&mut self) {
             self.cx.dispatch_action(self.window_id, HideDock);
         }