Rename extensionProvided and providingFeature properties of ConfigurationItem

Problem/Motivation

Currently the ConfigurationItem class includes these properties:

  /**
   * Whether the configuration is provided by an extension.
   *
   * @var bool
   */
  protected $extensionProvided = FALSE;

  /**
   * The providing feature.
   *
   * @var string
   */
  protected $providingFeature;

However:

• We set providingFeature for all extensions, not just features.
• In core, provider is used for a parallel case, EntityType::provider().
• extensionProvided is not strictly about whether the item is provided by an extension, but rather whether it has been explicitly excluded from packaging.

Proposed resolution

• Rename ConfigurationItem::providingFeature to ConfigurationItem::provider, and rename the corresponding getter and setter. Make appropriate changes to code documentation.
• Rename ConfigurationItem::extensionProvided to ConfigurationItem::excluded and rename the corresponding getter and setter.

Remaining tasks

User interface changes

API changes

Data model changes