Vocabularies are now configuration entities

As a part of #1802750: [Meta] Convert configurable data to ConfigEntity system

The {taxonomy_vocabulary} table is deprecated in favor of a new taxonomy_vocabulary config entity, but the table is preserved in installations upgraded from earlier versions of Drupal to allow contrib modules to migrate their data.

The vid column the {taxonomy_term_data} table is changed:

'vid' => array(
  'type' => 'int',
  'unsigned' => TRUE,
  'not null' => TRUE,
  'default' => 0,

'vid' => array(
  'type' => 'varchar',
  'length' => 255,
  'not null' => TRUE,
  'default' => '',

Functions removed:

• taxonomy_vocabulary_machine_name_load(), use Vocabulary::load($vid)
• views argument and filter for machine_name, use vid instead

To access a vocabulary's base properties use class methods $vocabulary->id() and $vocabulary->label()

// D7 code
$vocabulary = taxonomy_vocabulary_machine_name_load('forums');
$options[$vocabulary->vid] = $vocabulary->name;

// D8 code
use Drupal\taxonomy\Entity\Vocabulary;

$vocabulary = Vocabulary::load('forums');
$options[$vocabulary->id()] = $vocabulary->label();