Use the SDK's offline detection everywhere (except for restarting the sync loop). (#4472)

* Use the SDK's offline state to drive the offline indicator.

* Only use network reachability for restarting the sync loop, use the homeserver reachability for requests.

* Add a separate indicator to distinguish when the server is unreachable but the device is online.

ElementX/Sources/Other/NetworkMonitor/NetworkMonitor.swift

@@ -26,8 +26,10 @@ class NetworkMonitor: NetworkMonitorProtocol {
         pathMonitor.pathUpdateHandler = { [weak self] path in
             DispatchQueue.main.async {
                 if path.status == .satisfied {
+                    MXLog.info("Network reachability changed to reachable")
                     self?.reachabilitySubject.send(.reachable)
                 } else {
+                    MXLog.info("Network reachability changed to unreachable")
                     self?.reachabilitySubject.send(.unreachable)
                 }
             }