Allow arbitrary service to implement hooks

Problem/Motivation

📌 OOP hooks using event dispatcher Needs review provides a way to move hook implementations to services under the Drupal\module_name\Hook namespace (or subdirectory).

It would be great to allow any service (under any namespace) to implement hooks by adding attributes to their corresponding methods.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet