Revert InnoDB internal temporary tables from WL#7682

WL#7682 in MySQL 5.7 introduced the possibility to create light-weight temporary tables in InnoDB. These are called 'intrinsic temporary tables' in InnoDB, and in MySQL 5.7, they can be created by the optimizer for sorting or buffering data in query processing.
In MariaDB 10.2, the optimizer temporary tables cannot be created in InnoDB, so we should remove the dead code and related data structures.