Add rate limiter for S3 API layer (#9196)

- total number of S3 API calls per server
- maximum wait duration for any S3 API call

This implementation is primarily meant for situations
where HDDs are not capable enough to handle the incoming
workload and there is no way to throttle the client.

This feature allows MinIO server to throttle itself
such that we do not overwhelm the HDDs.

cmd/api-errors.go

@@ -211,6 +211,7 @@ const (
 	ErrInvalidResourceName
 	ErrServerNotInitialized
 	ErrOperationTimedOut
+	ErrOperationMaxedOut
 	ErrInvalidRequest
 	// MinIO storage class error codes
 	ErrInvalidStorageClass
@@ -1085,6 +1086,11 @@ var errorCodes = errorCodeMap{
 		Description:    "A timeout occurred while trying to lock a resource",
 		HTTPStatusCode: http.StatusRequestTimeout,
 	},
+	ErrOperationMaxedOut: {
+		Code:           "XMinioServerTimedOut",
+		Description:    "A timeout exceeded while waiting to proceed with the request",
+		HTTPStatusCode: http.StatusRequestTimeout,
+	},
 	ErrUnsupportedMetadata: {
 		Code:           "InvalidArgument",
 		Description:    "Your metadata headers are not supported.",