Support grouping by and aggregation on same column

Closes #3494340

src/Plugin/views/field/ViewsCsvField.php

@@ -74,7 +74,7 @@ class ViewsCsvField extends FieldPluginBase {
     $this->field_alias = $this->query->addField(
       $this->tableAlias,
       $this->options['key'],
-      '',
+      $this->getColumnAlias(),
       $this->options + $params,
     );
   }