[13.0.0] Remove the ability to change a group bundle type

Problem/Motivation

For our old group types we have a bunch of functionality that relates to changing the bundle of the group to move between the public, open, closed, and secret group types. For Flexible Groups this is no longer required as you can change the visibility of the group itself.

Steps to reproduce

Proposed resolution

Remove the code related to this functionality after deprecating it in 12.x

• Drupal\social_group\GroupContentVisibilityUpdate
• social_group_form_alter contains group type editing logic and references SocialGroupAddForm
• _social_group_inform_group_type_selection
• _social_group_type_edit_submit

Remaining tasks

User interface changes

API changes

Data model changes