- Disable the "prefer full scan on clustered primary key over full scan
of any secondary key" rule introduced by BUG#35850.
- Update test results accordingly
(bk trigger: file this for BUG#35850)
and auto_increment keys
Problems:
1. ALTER TABLE ... ORDER BY... doesn't make sence if there's a
user-defined clustered index in the table.
2. using a secondary index is slower than using a clustered one
for a table scan.
Fixes:
1. raise a warning.
2. use the clustered index.
