General: Add `allowed_blocks` field to block types

[jsnajdr]

There is a new block.json field called allowedBlocks, added in Gutenberg in ​https://github.com/WordPress/gutenberg/pull/58262. This is a companion patch to support this new field also on the server. It ensures that the following works:

1. If the allowedBlocks field is defined in block's block.json, the objects registered in WP_Block_Type_Registry will have the allowed_blocks field.
2. The allowed_blocks field is returned by the /wp/v2/block-types REST endpoint.
3. The allowedBlocks field will be included in the boostrapped block registration data in the unstable__bootstrapServerSideBlockDefinitions inline script.

There is a new block.json field called allowedBlocks, added in Gutenberg in ​https://github.com/WordPress/gutenberg/pull/58262. This is a companion patch to support this new field also on the server. It ensures that the following works:

1. If the allowedBlocks field is defined in block's block.json, the objects registered in WP_Block_Type_Registry will have the allowed_blocks field.
2. The allowed_blocks field is returned by the /wp/v2/block-types REST endpoint.
3. The allowedBlocks field will be included in the boostrapped block registration data in the unstable__bootstrapServerSideBlockDefinitions inline script.

Trac ticket: https://core.trac.wordpress.org/ticket/60403

allowed_blocks should be also explicitly defined in WP_Block_Type class.

allowed_blocks should be also explicitly defined in WP_Block_Type class.

Done ✅

CI is unhappy about something. Other than that, I have enough to commit it tomorrow.

[gziolo]

In 57521:

Editor: Add allowed_blocks field to block registration and REST API

There is a new block.json field called allowedBlocks, added in Gutenberg in ​https://github.com/WordPress/gutenberg/pull/58262. This adds support for this new field also on the server.

Props: gziolo, jsnajdr.
Fixes #60403.

Committed with https://core.trac.wordpress.org/changeset/57521.