A static cache of schema currentVersions per module.
Stores schema versions of the modules based on their defined hook_update_N implementations. Example: ``` [ 'example_module' => [ 8000, 8001, 8002 ] ] ```
Type: int[][]
\Drupal\Core\Update\UpdateHookRegistry::getAvailableUpdates()
protected $allAvailableSchemaVersions = [];