tests: Use explicit keywords args when calling initializers
tests: Use explicit keywords args when calling initializers

Replace all usage of GObject creation that relies on positional
arguments from overrides. Positional initializer args will be
deprecated, updating the tests as a first pass proves backwards
and forwards compatibility of the deprecation.

https://bugzilla.gnome.org/show_bug.cgi?id=705810

davibe/pygobject,sfeltman/pygobject,GNOME/pygobject,davibe/pygobject,pexip/pygobject,sfeltman/pygobject,GNOME/pygobject,pexip/pygobject,davibe/pygobject,pexip/pygobject,GNOME/pygobject,davibe/pygobject,sfeltman/pygobject