1.25.0_arenadata6

ADBDEV-2901 Fix order of restoring metadata  (#23)

Initially, gpbackup created consistent copies of databases, ordering
all object by oid, which created a correct sequence of objects. But in
ADBDEV-1973 (#9) the backup order was changed and the objects started to be
sorted by their size, which broke the logic of backup process. This
patch restores ordering by oid, but doesn't break order based on relation
size, because gpbackup stores two different lists of metadata and data
objects. This patch reorders metadata only, so all objects can be correclty
restored, but doesn't alter data objects order, so the data can be recovered
in any desired way.