appDisplay: CSS cleanup & fixes for app dialog

- change the container and dialog actor alignments
- pad the container to not have dialog overlap panel
- clean up extraneous app-folder css

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3044>

js/ui/appDisplay.js

@@ -2531,16 +2531,16 @@ export const AppFolderDialog = GObject.registerClass({
             style_class: 'app-folder-dialog',
             x_expand: true,
             y_expand: true,
-            x_align: Clutter.ActorAlign.FILL,
-            y_align: Clutter.ActorAlign.FILL,
+            x_align: Clutter.ActorAlign.CENTER,
+            y_align: Clutter.ActorAlign.CENTER,
             vertical: true,
         });
 
         this.child = new St.Bin({
             style_class: 'app-folder-dialog-container',
             child: this._viewBox,
-            x_align: Clutter.ActorAlign.CENTER,
-            y_align: Clutter.ActorAlign.CENTER,
+            x_align: Clutter.ActorAlign.FILL,
+            y_align: Clutter.ActorAlign.FILL,
         });
 
         this._addFolderNameEntry();