This change replaces the two columns rental_date and rental return in the
rental table with a single "rental_period" column which uses tsrange. This
commit also includes a new "legacy" schema, which gives us an example of a
non-default schema,  and a "rental" view within that schema which decomposes
the timestamp range column back into individual timestamp columns, in case
folks are looking at old material, or just cause non-range operators are
simpler imho. This also updates both data dumps to have the tsrange data.
Note, there are some spurious ordering changes as well, as we've dumped
everything with v14 pg_dump commands.