Allow Block layout to be translatable

Problem/Motivation

- Support translation import/export for layout in custom block.

Steps to reproduce

- Create a new custom block type.
- Enable layout builder on the custom block type
- Enable content translation
- Add a custom block for the new block type.
- Filled out all the required field.
- Now click on the layout tab and add new blocks.
- Save the layout builder content
- Click on translate
- Check languages and click request translation
- Throws an error saying the node id can't loaded.

Proposed resolution

- Make the code use entity vs the specific bundle type "node".

Remaining tasks

- Convert the code base to use entities instead of node.

User interface changes

- None.

API changes

- None.

Data model changes

- None