Add support to configure per-column statistics-gathering target while creating partition

[chopraanmol1]

When using a DDL query like following to set per-column statistics-gathering target on parent table, the equivalent targets are not set when a new paritition is created by partman.

ALTER TABLE <parent_table>
ALTER COLUMN <column 1> SET STATISTICS <some value>;

Ideally a new paritition should copy the per column statistic target from the parent table.

[keithf4]

I'll see about adding this into partman, however this really should be a request to core as well.