Review IDatetimeWidget dependencies for customization

[idgserpro]

If you don't have plone.app.contenttypes >= 1.1.1 installed, IDatetimeWidget comes from collective.z3cform.datetimewidget.

If you have plone.app.contenttypes >= 1.1.1 installed, plone.app.event 1.1.6 is installed as well and the IDatetimeWidget comes from plone.formwidget.datetime (because plone.app.event 1.1.6 installs it).

plone.formwidget.datetime is a merge of collective.z3cform.datetimewidget and archetypes.datetimewidget (which itself was derived from collective.z3cform.datetimewidget).

From plone.app.event > 1.2, plone.formwidget.datetime is removed:

dropped. The new plone.app.widgets package implements archetypes and z3cform

This issue was opened to discuss if it's possible to use just one widget dependency for all situations in the future, avoiding all this mess. Until this is done, multiple zcml registrations in https://github.com/collective/collective.cover/blob/059fecac5688c33859700e0352aaa6d99971af05/src/collective/cover/tiles/configuration_widgets/configure.zcml#L40,L45 will be done.