Refactor sidebar/tabs visibility to use GtkAction

* Add some actions for them to Glade file and make existing widgets
use these actions.
* Remove use of ignore_callback and some preferences globals and use
action instead.
* Centralize code related to showing/hiding sidebar widgets.
* Leave `interface_prefs.sidebar_symbol_visible` and
`interface_prefs.sidebar_openfiles_visible` and keep them up-to-date
for backwards compatibility.