Fix label in bulk epic edit and cross epic and epic work item

app/services/work_items/update_service.rb

ee/app/finders/ee/issuables/label_filter.rb

ee/app/graphql/ee/resolvers/bulk_labels_resolver.rb

ee/app/models/concerns/work_items/epic_as_work_item.rb

ee/app/models/ee/epic.rb

ee/app/models/ee/work_item.rb

ee/app/services/ee/issuable/bulk_update_service.rb

ee/lib/elastic/latest/epic_class_proxy.rb

ee/spec/services/ee/issuable/bulk_update_service_spec.rb

ee/spec/services/epics/update_service_spec.rb

ee/spec/services/work_items/update_service_spec.rb

..._examples/services/epic/sync_work_item_shared_examples.rb