Cleanup plugin deps and restrict symbols exported to plugins
I had this lingering as base for lock screen plugins that need to access functionality within phosh it's useful for !1359 (merged) as well so split this out:
- Restrict the symbols exported to plugins via a symbol map
- simplify plugin dependencies
- make sure we use the gtk_list_model symbols from phosh rather than building them into the plugins
EDIT: This will also help https://gitlab.com/mobian1/phog/-/issues/5
Edited by Guido Günther