feat: add explain ast insert queries test

tests/queries/0_stateless/03156_default_multiquery_split.reference

@@ -8,3 +8,7 @@ Syntax error
 7
 8
 9
+InsertQuery   (children 1)
+ Identifier TEST2
+InsertQuery   (children 1)
+ Identifier TEST1

tests/queries/0_stateless/03156_default_multiquery_split.sh

@@ -51,6 +51,13 @@ INSERT INTO TEST2 VALUES
 SELECT * FROM TEST1 ORDER BY value;
 SELECT * FROM TEST2 ORDER BY value;
 DROP TABLE TEST1; DROP TABLE TEST2;
+
+EXPLAIN AST INSERT INTO TEST2 FORMAT CSV
+1
+2
+
+EXPLAIN AST INSERT INTO TEST1 VALUES (101),(102);
+
 EOF
 
 $CLICKHOUSE_CLIENT -m < "$SQL_FILE_NAME"