pg_dumpall: Add --sequence-data.
I recently added this option to pg_dump, but I forgot to add it to
pg_dumpall, too. There's probably little use for it at the moment,
but we will need it if/when we teach pg_upgrade to use pg_dumpall
to dump the database schemas.
Oversight in commit
9c49f0e8cd.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aBE8rHFo922xQUwh%40nathan