Gets the intents whose groups count when computing visibility (Intent, a name or an array): View when absent;
All means every intent; an empty list means no group counts and all content is visible.
public IReadOnlyList<CosName> Intents { get; }
ISO 32000-2 §8.11.4.3, Table 99, and §8.11.2.3. In the default configuration it shall be View.