Flatten filterSet into only use

attribute/set.go

@@ -278,21 +278,13 @@ func NewSetWithSortableFiltered(kvs []KeyValue, tmp *Sortable, filter Filter) (S
 		// TODO (MrAlias): there is a potential optimization here where the
 		// filtering and uniquing are all done in the same step. For example:
 		// https://github.com/open-telemetry/opentelemetry-go/blob/228cc878a0f5de19290e8b2035dc4d0019f2a249/attribute/set.go#L266-L300
-		return filterSet(kvs, filter)
+		if div := filteredToFront(kvs, filter); div != 0 {
+			return Set{equivalent: computeDistinct(kvs[div:])}, kvs[:div]
+		}
 	}
 	return Set{equivalent: computeDistinct(kvs)}, nil
 }
 
-// filterSet reorders kvs so that included keys are contiguous at the end of
-// the slice, while excluded keys precede the included keys.
-func filterSet(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
-	k := filteredToFront(kvs, filter)
-	if k == 0 {
-		return Set{equivalent: computeDistinct(kvs)}, nil
-	}
-	return Set{equivalent: computeDistinct(kvs[k:])}, kvs[:k]
-}
-
 // filteredToFront filters slice in-place using f. All KeyValues that need to
 // be removed are moved to the front. All KeyValues that need to be kept are
 // moved (in-order) to the back. The index for the first KeyValue to be kept is