Increase network limits (#2796)

Fix max packet sizes

Fix max_payload_size function

Add merge block test

Fix max size calculation; fix up test

Clear comments

Add a payload_size_function

Use safe arith for payload calculation

Return an error if block too big in block production

Separate test to check if block is over limit

beacon_node/lighthouse_network/src/rpc/mod.rs

@@ -30,7 +30,7 @@ pub use methods::{
     RPCResponseErrorCode, RequestId, ResponseTermination, StatusMessage, MAX_REQUEST_BLOCKS,
 };
 pub(crate) use outbound::OutboundRequest;
-pub use protocol::{Protocol, RPCError};
+pub use protocol::{Protocol, RPCError, MAX_RPC_SIZE};
 
 pub(crate) mod codec;
 mod handler;