Remove Spatie\Newsletter dependency and fix marketing permissions

[ryanmitchell]

Ok, I've gone for the quickest option here, feel free to push back and tell me you dont like it @edalzell. I've pulled in the latest v4 Spatie classes and used them in our own Facade.

Fixes: https://github.com/statamic-rad-pack/mailchimp/issues/104 and https://github.com/statamic-rad-pack/mailchimp/issues/105

[edalzell]

SMORT