fix: various optimizations, idiomatic changes (#9179)

- acquire since leader lock for all background operations
  - healing, crawling and applying lifecycle policies.

- simplify lifecyle to avoid network calls, which was a
  bug in implementation - we should hold a leader and
  do everything from there, we have access to entire
  name space.

- make listing, walking not interfere by slowing itself
  down like the crawler.

- effectively use global context everywhere to ensure
  proper shutdown, in cache, lifecycle, healing

- don't read `format.json` for prometheus metrics in
  StorageInfo() call.

cmd/notification.go

@@ -267,24 +267,6 @@ func (sys *NotificationSys) BackgroundHealStatus() []madmin.BgHealState {
 	return states
 }
 
-// BackgroundOpsStatus - returns the status of all background operations of all peers
-func (sys *NotificationSys) BackgroundOpsStatus() []BgOpsStatus {
-	states := make([]BgOpsStatus, len(sys.peerClients))
-	for idx, client := range sys.peerClients {
-		if client == nil {
-			continue
-		}
-		st, err := client.BackgroundOpsStatus()
-		if err != nil {
-			logger.LogIf(context.Background(), err)
-		} else {
-			states[idx] = st
-		}
-	}
-
-	return states
-}
-
 // StartProfiling - start profiling on remote peers, by initiating a remote RPC.
 func (sys *NotificationSys) StartProfiling(profiler string) []NotificationPeerErr {
 	ng := WithNPeers(len(sys.peerClients))