Tidy up stale connections. (#406)

* If messageId changes and network ID doesn't, remove 'old' message_id

* Boot nodes/connection when no recent messages received for it

* Separate task needed for soketto recv to avoid cancel-safety issues with new interval

* Wee tidy up

* cargo fmt

* Add some logging around node adding/removing

* Another log info msg

* a bit of tidy up

* bump stale node timeout to 60s

backend/telemetry_shard/src/json_message/node_message.rs

@@ -246,7 +246,7 @@ pub struct NodeDetails {
     pub implementation: Box<str>,
     pub version: Box<str>,
     pub validator: Option<Box<str>>,
-    pub network_id: Option<Box<str>>,
+    pub network_id: node_types::NetworkId,
     pub startup_time: Option<Box<str>>,
 }