[#607] *: Use zap.Stringer() where possible

Semantic patch:
```
@@
var f expression
var t expression
var a expression
@@
 f(
    ...,
-    zap.String(t, a.String()),
+    zap.Stringer(t, a),
    ...,
)
```

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

pkg/local_object_storage/engine/remove_copies.go

@@ -55,7 +55,7 @@ func (e *StorageEngine) RemoveDuplicates(ctx context.Context, prm RemoveDuplicat
 	// This is not currently the case, because `FreeSpace` metric used by weight sorting is always 0.
 	// However we could change weights in future and easily forget this function.
 	for _, sh := range e.shards {
-		e.log.Debug(logs.EngineStartedDuplicatesRemovalRoutine, zap.String("shard_id", sh.ID().String()))
+		e.log.Debug(logs.EngineStartedDuplicatesRemovalRoutine, zap.Stringer("shard_id", sh.ID()))
 		ch := make(chan oid.Address)
 
 		errG, ctx := errgroup.WithContext(ctx)