[PP-1] Change the machine name of the 'create and edit custom blocks' permission

Problem/Motivation

In 📌 Rename Custom Block terminology in the admin UI Fixed we're making the following naming changes:

* renaming 'Custom Block' module to 'Block Content'
* renaming 'Custom block' entities as 'content blocks'
* renaming 'Custom block types' as 'Block types'

Layout builder has a permission with machine name 'create and edit custom blocks'

As we're moving to remove the word 'custom' we propose renaming this to 'create and edit inline content blocks'

Steps to reproduce

Proposed resolution

Decide if this is worthwhile, we've already changed the title - there is risk of disruption for any contrib module using that permission name

Add a new permission and deprecate the old one for removal in D11? Do we support deprecating permissions.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet