Enhancements to builder and adjuster annotations

This issue needs more work.

1) Some missing parts: update hook, config/schema changes.
2) Remove the 'internal' annotation, as I propose to get rid of SwiftmailerEmailBuilder anyway for ✨ Allow full management of override plugins Fixed .
3) Undo some changes to EmailFactory that might cause BC problems without any benefit.

This issue was committed in two parts. This patch (hopefully😃) represents the combined change from both commits.

Automatically closed - issue fixed for 2 weeks with no activity.