Drupal 7 has most global site and page elements hardwired into templates, and gives no control to users to move them around. All the page elements (title, tabs, actions, breadcrumb, messages) are hardwired to core and contrib themes alike. We should stop special-casing these, so they can be moved around and selectively hidden or replaced as needed.
- Introduce them as specific blocks that can be moved around.
- Remove special case items from themes.
- Introduce regions as needed to place these elements.
The code should depend on blocks as plugins (), however, we should not mark this postponed so we can do work on this in parallel and be ready for commits once that lands.