Use boost log attributes when logging RLPX handshake messages

[halfalicious]

There are a few pieces of information which are being manually logged in each RLPX handshake message:

• Was this connection initiated by the local node or a remote node i.e. connection direction ("egress" or "ingress")
• Remote node id (pubkey)
• Remote node address (if available i.e. if Aleth is still connected to the remote node)

Example log message:

TRACE 04-16 09:53:10 p2p rlpx auth to ##a979fb57…@52.16.188.185:30303

Manually logging this data in each message makes the log statements unnecessarily long - for example:

aleth/libp2p/RLPxHandshake.cpp

Lines 106 to 107 in aecf6c9

	LOG(m_logger) << connectionDirectionString() << "auth from " << m_remote << "@"
	<< m_socket->remoteEndpoint();

We should instead use boost logging attributes to automatically include this information in each log message. Details are available here:

• Clean up RLPX handshake logging #5568 (review)
• Clean up RLPX handshake logging #5568 (comment)