Support bucket versioning (#9377)

- Implement a new xl.json 2.0.0 format to support,
  this moves the entire marshaling logic to POSIX
  layer, top layer always consumes a common FileInfo
  construct which simplifies the metadata reads.
- Implement list object versions
- Migrate to siphash from crchash for new deployments
  for object placements.

Fixes #2111

pkg/madmin/info-commands.go

@@ -254,8 +254,8 @@ type FSBackend struct {
 	Type backendType `json:"backendType,omitempty"`
 }
 
-// XLBackend contains specific erasure storage information
-type XLBackend struct {
+// ErasureBackend contains specific erasure storage information
+type ErasureBackend struct {
 	Type         backendType `json:"backendType,omitempty"`
 	OnlineDisks  int         `json:"onlineDisks,omitempty"`
 	OfflineDisks int         `json:"offlineDisks,omitempty"`