Make it store its internal `zap.Logger`'s level. Also, make all the
components to accept internal `logger.Logger` instead of `zap.Logger`; it
will simplify future refactor.
Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
The service fetches tombstones from the network via object service, every
request is handled in the following order:
1. checks local LRU cache;
2. checks local storage engine;
3. tries to find object in the placement nodes.
Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
