date_type was replaced with timestamp_type, but it was very easy to
create a date_type instead of a timestamp_type by accident.
This patch changes the code so that a date_type is no longer
implicitly used when constructing a data_value. All existing code that
was depending on this is converted to explicitly using
date_type_native_type. A followup patch will convert to timestamp_type
when appropriate.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>