kv/RocksDBStore: Remove feature to make WholeSpaceIterator based on bounded iterator

kv/RocksDBStore: Remove feature to make WholeSpaceIterator based on bounded iterator

Iterator-bounding feature is introduced to make RocksDB iterators limited, so they
would less likely traverse over tombstones.
This is used when listing keys in fixed range, for example OMAPS for specific object.

It is problematic when extending this logic to WholeSpaceIterator,
since prefix must be taken into account.

Fixes: https://tracker.ceph.com/issues/55444
Signed-off-by: Adam Kupczyk <akupczyk@redhat.com>