Add an option to not automatically schedule content when creating through the calendar

Problem/Motivation

The content calendar has a way to add content on a certain day, which upon clicking automatically prefills the created date and scheduling date. Setting the scheduling date is something that can potentially be dangerous IMO: you're adding a draft to the calendar, forget about it for a while and at some point it will be automatically published. I think scheduling content for publishing should be a more conscious decision, something that should be configured once you're done with the article, not when creating your content planning.

Proposed resolution

Add a setting to automatically schedule content when creating through the calendar. Automatically turn it on for existing users for backwards compatibility reasons, but turn it off by default for new users.