fix: use internode data for DisksInfo, VolsInfo in message pack (#10821)

Similar to #10775 for fewer memory allocations, since we use
getOnlineDisks() extensively for listing we should optimize it
further.

Additionally, remove all unused walkers from the storage layer

cmd/storage-datatypes.go

@@ -22,6 +22,24 @@ import (
 
 //go:generate msgp -file=$GOFILE
 
+// DiskInfo is an extended type which returns current
+// disk usage per path.
+type DiskInfo struct {
+	Total     uint64
+	Free      uint64
+	Used      uint64
+	FSType    string
+	RootDisk  bool
+	Healing   bool
+	Endpoint  string
+	MountPath string
+	ID        string
+	Error     string // carries the error over the network
+}
+
+// VolsInfo is a collection of volume(bucket) information
+type VolsInfo []VolInfo
+
 // VolInfo - represents volume stat information.
 type VolInfo struct {
 	// Name of the volume.