[Proposal] Add an option whether to allow the partition column to be NULL

[xinyiZzz]

Is your feature request related to a problem? Please describe.
Strict data consistency is required in similar financial scenarios, when the partition column in the data is NULL, the import needs to report an error instead of the smallest partition, In relational databases support strong verification

Describe the solution you'd like
Add an option whether to allow the partition column to be NULL, When the option is enabled, the partition column must be NOT NULL when creating table, otherwise an error will be reported.