Update jetpack CLI command to generate new blocks using block.json

[jeherve]

Following #32697, we should encourage folks to use block.json to register new blocks in Jetpack. Updating the Jetpack CLI command would go a long way to do that:

jetpack/projects/plugins/jetpack/class.jetpack-cli.php

Lines 1919 to 1948 in a6a9739

	/**
	* Creates the essential files in Jetpack to start building a Gutenberg block or plugin.
	*
	* ## TYPES
	*
	* block: it creates a Jetpack block. All files will be created in a directory under extensions/blocks named based on the block title or a specific given slug.
	*
	* ## BLOCK TYPE OPTIONS
	*
	* The first parameter is the block title and it's not associative. Add it wrapped in quotes.
	* The title is also used to create the slug and the edit PHP class name. If it's something like "Logo gallery", the slug will be 'logo-gallery' and the class name will be LogoGalleryEdit.
	* --slug: Specific slug to identify the block that overrides the one generated based on the title.
	* --description: Allows to provide a text description of the block.
	* --keywords: Provide up to three keywords separated by comma so users can find this block when they search in Gutenberg's inserter.
	* --variation: Allows to decide whether the block should be a production block, experimental, or beta. Defaults to Beta when arg not provided.
	*
	* ## BLOCK TYPE EXAMPLES
	*
	* wp jetpack scaffold block "Cool Block"
	* wp jetpack scaffold block "Amazing Rock" --slug="good-music" --description="Rock the best music on your site"
	* wp jetpack scaffold block "Jukebox" --keywords="music, audio, media"
	* wp jetpack scaffold block "Jukebox" --variation="experimental"
	*
	* @subcommand scaffold block
	* @synopsis <type> <title> [--slug] [--description] [--keywords] [--variation]
	*
	* @param array $args Positional parameters, when strings are passed, wrap them in quotes.
	* @param array $assoc_args Associative parameters like --slug="nice-block".
	*/
	public function scaffold( $args, $assoc_args ) {

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Primary issue: #32602