Core issue patternfly/patternfly#7544

I believe all that's needed is

• Adds .pf-m-expandable to the __field-group element that serves as the opt-in for this animation
• __field-group-body is currently the "expanded content" and is conditionally rendered. If a user has opted in to the animation, we should always render that element and add inert when the field group is not expanded
• In a future breaking change release, we'll want to
  • Add .pf-m-expandable to all expandable field groups
  • Always render __field-group-body in an expandable field group