Support inline blocks in layout

Problem/Motivation

I suggest supporting adding inline blocks in the predefined layouts, so when creating a new node using this layout it will automatically create a clone for the existing inline blocks in the layout.

Steps to reproduce

1- Create a custom block called accordion.
2- Create a custom block called accordion section.
3- Add entity reference field to the accordion block to reference the accordion section block.
4- Create a new layout from layout library.
5- Add an accordion block to a section.
6- Create a node with the created layout.
7- It will create the accordion block but it will keep using the original accordion sections (inline-block) that are used in the layout.

Proposed resolution

I suggest updating the event subscriber to clone the section deeply with any inline blocks used in it.

Remaining tasks

User interface changes

API changes

Data model changes