Move configuration to Drupal core permissions user interface

Problem/Motivation

The Content Access permissions under a content type like Article are shown as individual lists, but Drupal core is using a grid display, for example under Administration > Structure > Content types > Article > Manage permissions.

Also, there is an incomplete overlap, where some Drupal core options are included, others are not. It seems like these are the Drupal core permissions:

• Article: Create new content
• Article: Delete any content
• Article: Delete own content
• Article: Delete revisions
• Article: Edit any content
• Article: Edit own content
• Article: Revert revisions
• Article: View revisions

These are Content Access permissions (renamed to match core, i.e. from "View any article content"):

• Article: Delete any content
• Article: Delete own content
• Article: Edit any content
• Article: Edit own content
• Article: View any content
• Article: View own content

Overlapping permissions:

• Article: Delete any content
• Article: Delete own content
• Article: Edit any content
• Article: Edit own content

Unique permissions for Content Access

• Article: View any content
• Article: View own content

PS. Shouldn't there be a 2.1.x-dev branch, since there is a 2.1.0-rc1 release?

Steps to reproduce

Want to use the newly available permissions, have a bit of a hard time finding them under each content type, and then see some overlap.

Proposed resolution

We could streamline the permission user experience, by altering the Drupal core Permissions page (/admin/people/permissions) and instead add the Content Access UI elements there.

For minimal disturbance, we could do it in two phases:

1. Add the Content Access elements to the Drupal core permissions page UI until we have feature parity
2. When it's tested and ready, we could remove the custom Content Access UI under the "Access control" tab

Remaining tasks

Phase #1: Add to Drupal core Permissions page

• 🔲 Add the Content Access permissions elements to the Drupal core Permissions page UI (/admin/people/permissions)
• 🔲 Make sure wording is aligned with Drupal core
• 🔲 Adjust tests, delete or add new ones as needed

Phase #2: Remove Content Access UI

• 🔲 After a while in use, remove the custom Content Access UI shown under the "Access control" tab for each content type
• 🔲 Adjust tests and delete unneeded ones
• 🔲 Update documentation in README.md shown under https://git.drupalcode.org/project/content_access
• 🔲 Archive https://www.drupal.org/docs/7/modules/content-access

(Replace as tasks are done ✅)

User interface changes

• The Content Access permissions are added to the standard Drupal core Permission page (/admin/people/permissions)
• The custom Content Access configuration under each content type is removed (the "Access control" tab)

API changes

Data model changes