support external address in discv4 handle type

[mattsse]

Describe the feature

currently the shared local address is constant

reth/crates/net/discv4/src/lib.rs

Lines 131 to 132 in 7cd7859

	/// The address of the udp socket
	local_addr: SocketAddr,

this should also support the external IP:

reth/crates/net/discv4/src/lib.rs

Lines 516 to 523 in 7cd7859

	pub fn set_external_ip_addr(&mut self, external_ip: IpAddr) {
	if self.local_node_record.address != external_ip {
	debug!(target : "discv4", ?external_ip, "Updating external ip");
	self.local_node_record.address = external_ip;
	let _ = self.local_eip_868_enr.set_ip(external_ip, &self.secret_key);
	debug!(target : "discv4", enr=?self.local_eip_868_enr, "Updated local ENR");
	}
	}

Additional context

No response