[master] Do Automatic Volume Grow in background (#5781)

* Do Automatic Volume Grow in backgound

* pass lastGrowCount to master

* fix build

* fix count to uint64

weed/topology/topology_info.go

@@ -42,6 +42,15 @@ func (t *Topology) ToInfo() (info TopologyInfo) {
 	return
 }
 
+func (t *Topology) ListVolumeLyauts() (volumeLayouts []*VolumeLayout) {
+	for _, col := range t.collectionMap.Items() {
+		for _, volumeLayout := range col.(*Collection).storageType2VolumeLayout.Items() {
+			volumeLayouts = append(volumeLayouts, volumeLayout.(*VolumeLayout))
+		}
+	}
+	return volumeLayouts
+}
+
 func (t *Topology) ToVolumeMap() interface{} {
 	m := make(map[string]interface{})
 	m["Max"] = t.diskUsages.GetMaxVolumeCount()