fix(tags) use entity count as entity index

For tag-filtered queries in Cassandra, use the current entity count as
the entity table index rather than the row iteration counter. If some
entities are excluded from the table, this ensures that no table indices
have a nil value. Kong Enterprise filters these results to exclude
entities in other workspaces.

kong/db/strategies/cassandra/init.lua

@@ -1142,8 +1142,8 @@ do
           clear_tab(current_entity_ids)
           current_entity_count = 0
           for i, row in ipairs(rows) do
-            current_entity_ids[i] = row.entity_id
             current_entity_count = current_entity_count + 1
+            current_entity_ids[current_entity_count] = row.entity_id
           end
         end
       end