Add self-healing feature (#7604)

- Background Heal routine receives heal requests from a channel, either to
heal format, buckets or objects
- Daily sweeper lists all objects in all buckets, these objects
don't necessarly have read quorum so they can be removed if
these objects are unhealable
- Heal daily ops receives objects from the daily sweeper
and send them to the heal routine.

cmd/test-utils_test.go

@@ -470,6 +470,9 @@ func resetGlobalStorageEnvs() {
 
 // reset global heal state
 func resetGlobalHealState() {
+	if globalAllHealState == nil {
+		return
+	}
 	globalAllHealState.Lock()
 	defer globalAllHealState.Unlock()
 	for _, v := range globalAllHealState.healSeqMap {