kad: Include a timeout for QueryExecutor::send_message

[lexnv]

Sending a plain message using the query executor does not take into account timeouts:

litep2p/src/protocol/libp2p/kademlia/executor.rs

Lines 136 to 139 in e3a22d5

	pub fn send_message(&mut self, peer: PeerId, message: Bytes, mut substream: Substream) {
	self.futures.push(Box::pin(async move {
	match substream.send_framed(message).await {
	Ok(_) => QueryContext {

The other methods of the query executor bound the total time to the READ_TIMEOUT constant:

litep2p/src/protocol/libp2p/kademlia/executor.rs

Lines 161 to 166 in e3a22d5

	match tokio::time::timeout(READ_TIMEOUT, substream.next()).await {
	Err(_) => QueryContext {
	peer,
	query_id,
	result: QueryResult::Timeout,
	},

Introduce a new variable WRITE_TIMEOUT and ensure writes are timedout as well.