The 10.5 version of the patch.
Removing DEFAULT from INFORMATION_SCHEMA columns.
DEFAULT in read-only tables is rather meaningless.
Upgrade should go smoothly.
Also fixes:
MDEV-20254 Problems with EMPTY_STRING_IS_NULL and I_S tables
In rare cases, both listener and worker can do poll at the same time
(one of them will return events, another one no events)
Fix test query to account for it.