Refactor display page and removed the empty behavior plugin

config/schema/facetapi.facet.schema.yml

css/facetapi.admin.css

facetapi.services.yml

src/Annotation/FacetApiEmptyBehavior.php

src/EmptyBehavior/EmptyBehaviorInterface.php

src/EmptyBehavior/EmptyBehaviorPluginBase.php

src/EmptyBehavior/EmptyBehaviorPluginManager.php

src/Entity/Facet.php

src/FacetInterface.php

src/FacetManager/DefaultFacetManager.php

src/Form/FacetDisplayForm.php

src/Form/FacetForm.php

src/Plugin/facetapi/empty_behavior/EmptyBehaviorNone.php

src/Plugin/facetapi/empty_behavior/EmptyBehaviorText.php

src/Plugin/facetapi/processor/MinimumCountProcessor.php

...gin/facetapi/processor/UidToUserNameCallbackProcessor.php

src/Tests/IntegrationTest.php

...src/Unit/EmptyBehavior/EmptyBehaviorPluginManagerTest.php