[#191] engine: Allow to remove redundant object copies

RemoveDuplicates() removes all duplicate object copies stored on
multiple shards. All shards are processed and the command tries to leave
a copy on the best shard according to HRW.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/engine/engine.go

@@ -17,6 +17,8 @@ import (
 type StorageEngine struct {
 	*cfg
 
+	removeDuplicatesInProgress atomic.Bool
+
 	mtx *sync.RWMutex
 
 	shards map[string]hashedShard