before this change, we assume that generation is always integer based.
in order to enable the UUID-based generation identifier if the related
option is set, we should populate this option down to generation generator.
because we don't have access to the cluster features in some places where
a new generation is created, a new accessor exposing feature_service from
sstable manager is added.
Fixes#10459
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
939fa087cc