[UX] When a new content type is created, automatically assign permissions to the "Editor" role

Description of the need

This is a sibling issue to #5350, and this is a related issue against Drupal 7 core: Dynamic permissions cannot be automatically assigned to or removed from roles.

The 3 content types that come OOTB with a default Backdrop installation all have these permissions already granted to the Editor role, but that is not the case when creating new content types:

When creating a new content type, these permissions need to be manually adjusted each time. With #900, we have improved the UX in Backdrop, since you don't need to navigate away from the content type creation/edit form in order to assign the required permissions to the various roles, nor do you have to search through a HUGE list of permissions to find the correct ones ...this issue here is to improve the UX a big further, by allowing some sensible defaults (that way, site builders will have to scroll/click less when configuring content types).

Proposed solution

• Automatically grant these permissions to the Editor role.
• Perhaps add a setting for this in admin/config/people/roles, similar to the "The role that will be automatically assigned new permissions whenever a module is enabled:" setting for admin roles.
• Also throw a notice/info message in the node creation form, letting the user know that automatic permissions assignment has happened, and that they might want to review/tweak them as needed.

Advocate for this feature: @klonos