chore: use extend instead of manual loop in multi group by (apache#19429)

## Which issue does this PR close?

N/A

## Rationale for this change

using more efficient extend

## What changes are included in this PR?

replace manual loop with `extend`

## Are these changes tested?

existing tests

## Are there any user-facing changes?

Nope

Author: rluvaton

datafusion/physical-plan/src/aggregates/group_values/multi_group_by/mod.rs

@@ -540,14 +540,13 @@ impl<const STREAMING: bool> GroupValuesColumn<STREAMING> {
                 // into `vectorized_equal_to_row_indices` and `vectorized_equal_to_group_indices`.
                 let list_offset = group_index_view.value() as usize;
                 let group_index_list = &self.group_index_lists[list_offset];
-                for &group_index in group_index_list {
-                    self.vectorized_operation_buffers
-                        .equal_to_row_indices
-                        .push(row);
-                    self.vectorized_operation_buffers
-                        .equal_to_group_indices
-                        .push(group_index);
-                }
+
+                self.vectorized_operation_buffers
+                    .equal_to_group_indices
+                    .extend_from_slice(group_index_list);
+                self.vectorized_operation_buffers
+                    .equal_to_row_indices
+                    .extend(std::iter::repeat_n(row, group_index_list.len()));
             } else {
                 let group_index = group_index_view.value() as usize;
                 self.vectorized_operation_buffers