Add a constructor to WP_REST_Settings_Controller

[Soean]

The classWP_REST_Settings_Controller overrides the properties namespace and rest_base.
Instead, the properties should be set by a constructor.

[Soean]

Adds a constructor to WP_REST_Settings_Controller.

[Soean]

Adds a constructor to WP_REST_Settings_Controller.

[Soean]

Ups. 38429.patch is the right patch.

[Soean]

All the other controller classes have a constructor to set the properties. So we should use it in WP_REST_Settings_Controller too, to be consistent in the classes.

[rachelbaker]

In 38954:

REST API: Add constructor to the WP_REST_Settings_Controller class.

Provides consistency with the other API endpoint controller classes.

Props Soean.
Fixes #38429.