Adjust Layout Builder permission checking for inline blocks once more granular block permissions exist

Problem/Motivation

We currently have granular inline block permissions in Drupal, allowing to precisely set which custom block bundles can be created / edited by which user role. Unfortunately, restricting access to certain custom block types doesn't work in Layout Builder that allows to add / edit all or nothing within a layout by design.

Proposed resolution

1. Add a new permission create and edit accessible custom blocks.
2. Restrict custom blocks list in LB to only those accessible ones for users having only that permission and not create and edit custom blocks
3. Alter LB block add, edit and delete route access basing on custom block permissions for the current user and the old / new permission.
4. (Of course) Add automated test coverage.
5. Create a follow-up to remove the old permission and make LB always respect block access logic or at least mark the old permission with restrict access: true

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet