When editing a content type the machine name should not automatically update as the display name is changed

On the first submission of a content type form, automatically suggesting a machine name based on a display name is a great help. On subsequent edits of this form, however, changing the machine name when the display name is edited is a detriment to usability and simply dangerous for existing theming and custom code.

#302054 was approved in part on condition of this change-on-edit behavior not being present, but that is the current behavior.