Block Template Validation Improvements

[BE-Webdesign]

Description

Template validation for nested templates is currently not working cleanly noted here: #11681. In depth details can be read here: #11681 (comment)

More background:
#3588

Tasks:

1. • Perform template validation in the BlockList component.
     • Add the global template settings under the blockListSettings state
     • Local templates should take precedence over the global template.
     • Create logic which also parses the global template given an arbitrary client ID.
2. • Remove block validation from the BlockEditorProvider level in favor of 1.
     • Make sure that the notice on invalid template still displays and works properly
3. • Remove block validation from InnerBlocks in favor of 1.
4. • (future) Create a new way to consume this API in order to power things like isMovable, isLocked, etc. etc. It should be more specific and consistent so that it's easy to modify the block actions available based on the template.

How has this been tested?

Tests in progress...

Screenshots

In progress...

Types of changes

In progress...

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR. .

[BE-Webdesign]

Closing as this is long stale.