In some scenarios, when users use dynamic partitions, they hope to use Doris' hierarchical storage
function at the same time.
For example, for the dynamic partition rule of partitioning by day, we hope that the partitions of the last 3 days
are stored on the SSD storage medium and automatically migrated to the HDD storage medium after expiration.
This CL add a new dynamic partition property: "hot_partition_num".
This parameter is used to specify how many recent partitions need to be stored on the SSD storage medium.
510606ddd4