When perform_cleanup adds sstables to sstables_requiring_cleanup,
also save the owned_ranges_ptr in the compaction_state so
it could be used by other compaction types like
regular, reshape, or major compaction.
When the exhausted sstables are released, check
if sstables_requiring_cleanup is empty, and if it is,
clear also the owned_ranges_ptr.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>