Introduce and make use of NodePreview enum, to replace node related usage of DRUPAL_DISABLED, DRUPAL_OPTIONAL and DRUPAL_REQUIRED constants

Problem/Motivation

Split from 📌 Each class using DRUPAL_* constants from system.module should define its own constants Needs work

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet