opt: implement region-column inference

This commit finishes the implementation for the new storage parameter
`infer_rbr_region_col_using_constraint`. If a foreign key constraint
is specified via that setting, the constraint will be used to plan
a lookup join into the parent table to retrieve the correct values for
the region column on INSERT, UPDATE, and UPSERT operations. This will
make it easier for customers to add the `crdb_region` column to their
foreign-key constraints, since they no longer have to guarantee that
an insert into the child table happens in the same region as the
matching parent row.

Fixes #148243

Release note (sql change): Added support for automatically determining
the region column for a REGIONAL BY ROW table using a foreign key constraint.
The foreign key is specified by setting a new table storage parameter
`infer_rbr_region_col_using_constraint`, and must contain the region
column. This can be useful for applications that are unable to guarantee
that a child row is inserted or updated from the same region as the
matching parent row.

Author: DrewKimball