Tree / Playlist Viewer / Menu: Fix redraw issues

1) Tree_lists was only initialized when booting the player.

In cases where a skin used custom UI viewports of
different sizes, when switching between screens, such as
between root menu, QuickScreen, and tree browser, this
caused list titles to appear with a significant delay,
unless a GUI_EVENT_ACTIONUPDATE was sent.

Tree_lists is now initialized when entering dirbrowse
or when restoring/reloading the list.

This eliminates multiple redundant UI refreshes when
entering the tree browser, due to gui_synclist_draw not
being called twice anymore and by being able to omit
GUI_EVENT_ACTIONUPDATE.

Separate calls to gui_synclist_init_display_settings
have become unnecessary since it is already called
by gui_synclist_init.

2) The synclist is also re-initialized when returning
from the QuickScreen in the Playlist Viewer or
regular menus, or when returning from Settings
menus

Change-Id: I2884249eda55f782e97abad9dc19b3d9d1267fc9

apps/main.c

@@ -167,7 +167,7 @@ int main(void)
         screens[i].update();
     }
     list_init();
-    tree_gui_init();
+    tree_init();
     /* Keep the order of this 3
      * Must be done before any code uses the multi-screen API */
 #ifdef HAVE_USBSTACK