BUG: Associate default icon with all modules.

Doing so will allow module to be added to the module toolbar by updating
the list of favorite modules in the application settings.

Fixes #3293

Co-authored-by: Julien Finet <julien.finet@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22288 3bd1e089-480b-0410-8dfb-8563597acbee