feat: Single drive XL implementation (#14970)

Main motivation is move towards a common backend format
for all different types of modes in MinIO, allowing for
a simpler code and predictable behavior across all features.

This PR also brings features such as versioning, replication,
transitioning to single drive setups.

cmd/metrics-v2.go

@@ -1365,7 +1365,7 @@ func getMinioHealingMetrics() *MetricsGroup {
 	mg := &MetricsGroup{}
 	mg.RegisterRead(func(_ context.Context) (metrics []Metric) {
 		metrics = make([]Metric, 0, 5)
-		if !globalIsErasure {
+		if globalIsGateway {
 			return
 		}
 		bgSeq, exists := globalBackgroundHealState.getHealSequenceByToken(bgHealingUUID)
@@ -1817,7 +1817,7 @@ func getClusterStorageMetrics() *MetricsGroup {
 	mg.RegisterRead(func(ctx context.Context) (metrics []Metric) {
 		objLayer := newObjectLayerFn()
 		// Service not initialized yet
-		if objLayer == nil || !globalIsErasure {
+		if objLayer == nil || globalIsGateway {
 			return
 		}