[#1024] shard: Resync metabase concurrently

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/shard/shard.go

@@ -95,7 +95,8 @@ type MetricsWriter interface {
 type cfg struct {
 	m sync.RWMutex
 
-	refillMetabase bool
+	refillMetabase             bool
+	refillMetabaseWorkersCount int
 
 	rmBatchSize int
 
@@ -300,6 +301,13 @@ func WithRefillMetabase(v bool) Option {
 	}
 }
 
+// WithRefillMetabaseWorkersCount returns option to set count of workers to refill the Metabase on Shard's initialization step.
+func WithRefillMetabaseWorkersCount(v int) Option {
+	return func(c *cfg) {
+		c.refillMetabaseWorkersCount = v
+	}
+}
+
 // WithMode returns option to set shard's mode. Mode must be one of the predefined:
 //   - mode.ReadWrite;
 //   - mode.ReadOnly.