Clear and reregister devices for atmos alarms (#11391)

* deregister sensors upon device list update and re-register after clearing devices

* fire alarms, too

* adds the last set of known devices to the device list update event

* update UI upon clearing everything out

* addresses reviews

Content.Server/Atmos/Monitor/Systems/AtmosDeviceNetwork.cs

@@ -15,6 +15,11 @@ public sealed class AtmosDeviceNetworkSystem : EntitySystem
     /// </summary>
     public const string RegisterDevice = "atmos_register_device";
 
+    /// <summary>
+    ///     Deregister a device's address on this device.
+    /// </summary>
+    public const string DeregisterDevice = "atmos_deregister_device";
+
     /// <summary>
     ///     Synchronize the data this device has with the sender.
     /// </summary>
@@ -32,6 +37,16 @@ public sealed class AtmosDeviceNetworkSystem : EntitySystem
         _deviceNet.QueuePacket(uid, address, registerPayload);
     }
 
+    public void Deregister(EntityUid uid, string? address)
+    {
+        var deregisterPayload = new NetworkPayload
+        {
+            [DeviceNetworkConstants.Command] = DeregisterDevice
+        };
+
+        _deviceNet.QueuePacket(uid, address, deregisterPayload);
+    }
+
     public void Sync(EntityUid uid, string? address)
     {
         var syncPayload = new NetworkPayload