ContentEntityType and ConfigEntityType objects and annotations have been added

Previously, all entity types used the @EntityType annotation and EntityType object (to get entity type definition). Now ConfigEntityType and ContentEntityType annotations and entity type objects have been added to provide better default values and more specific/descriptive annotations.

ConfigEntityStorage is added as the default storage for entity types that use @ConfigEntityType, so is no longer needed in the annotation unless it is being overridden. Similar for @ContentEntityType, ContentEntityDatabaseStorage is the default storage implementation then.

Use it like this:

/**
 * Defines a Block configuration entity class.
 *
 * @ConfigEntityType(
 *   id = "block",
 *   label = @Translation("Block"),
 *   controllers = {
 *     "access" = "Drupal\block\BlockAccessControlHandler",
 *     "view_builder" = "Drupal\block\BlockViewBuilder",
 *     ...
 * )
 */