This includes
- rename namespace in snapshot-ctl.[cc|hh]
- move methods from storage_service to snapshot_ctl
- move snapshot_details struct
- temporarily make storage_service._snapshot_lock and ._snapshot_ops public
- replace two get_local_storage_service() occurrences with this._db
The latter is not 100% clear as the code that does this references "this"
from another shard, but the _db in question is the distributed object, so
they are all the same on all instances.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
d674baacef