Add a limit to the cross-chain messages submitted

[en]

see snowfork:

134         /// Submit message on the outbound channel
135         pub fn submit(who: &T::AccountId, target: H160, payload: &[u8]) -> DispatchResult {
140                 ensure!(
141                         MessageQueue::decode_len().unwrap_or(0) < T::MaxMessagesPerCommit::get(),
142                         Error::<T>::QueueSizeLimitReached,
143                 );
144                 ensure!(
145                         payload.len() <= T::MaxMessagePayloadSize::get(),
146                         Error::<T>::PayloadTooLarge,
147                 );