Rate limit WebSocket messages

[jondubois]

Story
As a node user, I would like to restrict traffic/ messages which I receive from any peer so that I can be safeguarded from the spamming.

Acceptance Criteria

1. Accept messages/ transaction blocks from each peer when it is not exceeded your Rate limit.
2. If a specific peer is reached his maximum Rate limit, then the specific peer connection should be interrupted.
3. The rate limit (receiving limit) can vary from peer to peer.

Expected behavior

There should be a simple rate-limiting mechanism to prevent nodes from spamming our WebSocket connection.

Actual behavior

There is no rate limiting to prevent remote clients from spamming a node's WebSocket connection.

If we have a sufficiently large machine (or multiple machines), we can spam a specific node with WebSocket messages to make it consume CPU.