fix: allow accountInfo, addUser and getUserInfo implicit (#10978)

- accountInfo API that returns information about
  user, access to buckets and the size per bucket
- addUser - user is allowed to change their secretKey
- getUserInfo - returns user info if the incoming
  is the same user requesting their information

pkg/madmin/examples/accounting-info.go

@@ -37,10 +37,10 @@ func main() {
 		log.Fatalln(err)
 	}
 
-	accountUsageInfo, err := madmClnt.AccountUsageInfo(context.Background())
+	accountInfo, err := madmClnt.AccountInfo(context.Background())
 	if err != nil {
 		log.Fatalln(err)
 	}
 
-	log.Println(accountUsageInfo)
+	log.Println(accountInfo)
 }