Remove legacy hook functionality without breaking API

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | na
| Refs tickets  | na
| License       | MIT
| Doc PR        | na

This would be a slightly accelerated BC break, but I don't think any modules for 1.3 actually use this API anyway.
Removal now simplifies certain tasks for me.