DROP PARTITION, CONVERT OUT require both ALTER and DROP privileges

Precise user management requires fine privilege separation. Now DROP PARTITION requires both ALTER and DROP which allows users that do DROP PARTITION to do also any other DDL changes.

TRUNCATE PARTITION requires only DROP privilege and that makes sense. Users allowed to drop the table also should be allowed to drop the data by parts, either by the partition or by the data inside the partition.

Now DROP PARTITION should be allowed only be DROP privilege. The same with CONVERT OUT as it drops partition and creates a table, it must not require ALTER privilege.