6 files declare their use of BuildProcessorInterface in Facets 8

DefaultFacetsSummaryManager.php in modules/facets_summary/src/FacetsSummaryManager/DefaultFacetsSummaryManager.php

HideWhenNotRenderedProcessor.php in modules/facets_summary/src/Plugin/facets_summary/processor/HideWhenNotRenderedProcessor.php

ResetFacetsProcessor.php in modules/facets_summary/src/Plugin/facets_summary/processor/ResetFacetsProcessor.php

ShowCountProcessor.php in modules/facets_summary/src/Plugin/facets_summary/processor/ShowCountProcessor.php

ShowSummaryProcessor.php in modules/facets_summary/src/Plugin/facets_summary/processor/ShowSummaryProcessor.php

ShowTextWhenEmptyProcessor.php in modules/facets_summary/src/Plugin/facets_summary/processor/ShowTextWhenEmptyProcessor.php