[Maria-developers] MDEV-11245 Move prepare_create_field and sp_prepare_create_field() as methods to Column_definition

Hello Sanja, can you please review a patch for MDEV-11245 for 10.3? It's a small refactoring intended to make patches for these tasks look better: - MDEV-10577 sql_mode=ORACLE: %TYPE in variable declarations - MDEV-10914 ROW data type for stored routine variables Thanks!