Centralize icon definitions #114
Description
When the same icon is used in multiple places, we should define the icon once and reuse that definition (if possible), so that we can centrally change the icon or its attributes if necessary. E.g. {{msc.trash}} is used in multiple places, and we may decide to use a different delete icon in the future
See {{widgets/init.py::SEVERITY_ICONS}} for an example of how this can be done