Allow 'Groups' to be set to 'All Public Groups'

1.0 Problem/Motivation

Even with the new 'toggle' option explained at https://github.com/colemanw/webform_civicrm/pull/640 it seems clunky if one want to have a dynamic listing of ONLY public groups (which is pretty much what a Subscribe page should be doing)

2.0 Detailed steps to reproduce (embed screenshots)

Set Groups to 'user select'

Currently one can then set the Drupal webform component to be STATIC and select all Public Groups (this could be a large list within a huge list)

3.0 Proposed resolution

That you accept https://github.com/colemanw/webform_civicrm/pull/640 with the tiny (?) tweak requested at

Can you please rename to:

- User Select -
- User Select (public groups) -

JItendra asked me to open as a new Issue - i don't really understand why instead of just re-opening 640 with the requested changes.