Follow up of PLANET-3264

The scripts that convert the old blocks to new blocks have been delivered as wp-cli commands.

Please study the functions that were created for that task, and create an admin menu (under tools, or create a menu item and put the new one and the plugin-blocks-report under it), where an administrator of wordpress can click on a button that will replace all old blocks with the new ones, with the same way the wp-cli command does.