Testing for MDEV-8989

test this tree:
https://github.com/MariaDB/server/commits/bb-10.1-mdev8989

for crashes and wrong query results?

things to test for

• ORDER BY/GROUP BY with various columns
• WHERE clause should have equalities involving the same columns
• there should be indexes that allow to resolve ORDER/GROUP BY and use the same
  columns. Try without these indexes, too.

• VIEWS with algorithm=merge receive a slightly different handling in the
  patch, so it would be nice to cover them,too.