[Maria-developers] MDEV-12775 Reuse data type aggregation code for hybrid functions and UNION

Hello Sanja, Please review a patch for MDEV-12775, also fixing a number of bugs: - MDEV-9495 Wrong field type for a UNION of a signed and an unsigned INT expression - MDEV-9497 UNION and COALESCE produce different field types for DECIMAL+INT - MDEV-12594 UNION between fixed length double columns does not always preserve scale - MDEV-12595 UNION converts INT to BIGINT - MDEV-12599 UNION is not symmetric when mixing INT and CHAR Thanks!