In this commit, I copied the code for processing the rendering of emails
from the current renderer.
This will allow us to use different base templates and styles.
Ideally, we should be able to add hooks and reuse the renderer from the engine namespace in
the current renderer.
[MAILPOET-5540]
This changes how the editor is initialized. The integration initialization class
doesn't get the engine class anymore, but integration is initialized via
mailpoet_email_editor_initialized action triggered from the engine.
This allows multiple integrations to hook into the engine.
[MAILPOET-5540]
