fix(dup): last_connection / last_disconnection timestamp unit

timestamps were in millisecond precision, but `DateTime.from_unix!` was
given microsecond precision. This caused datetimes to be incorrect.

this was the result after setting up astarte in 5 minutes and running
astarte-stream-qt5-test

```
❯ docker compose exec -it scylla cqlsh -e 'select last_connection from test.devices;'

 last_connection
---------------------------------
 1970-01-21 03:48:22.216000+0000
```

Signed-off-by: Francesco Noacco <francesco.noacco@secomind.com>

Author: noaccOS

apps/astarte_data_updater_plant/lib/astarte_data_updater_plant/data_updater/impl.ex

@@ -130,7 +130,7 @@ defmodule Astarte.DataUpdaterPlant.DataUpdater.Impl do
     Queries.set_device_connected!(
       new_state.realm,
       new_state.device_id,
-      DateTime.from_unix!(timestamp_ms, :microsecond),
+      DateTime.from_unix!(timestamp_ms, :millisecond),
       ip_address
     )
 
@@ -2244,7 +2244,7 @@ defmodule Astarte.DataUpdaterPlant.DataUpdater.Impl do
     Queries.set_device_disconnected!(
       state.realm,
       state.device_id,
-      DateTime.from_unix!(timestamp_ms, :microsecond),
+      DateTime.from_unix!(timestamp_ms, :millisecond),
       state.total_received_msgs,
       state.total_received_bytes,
       state.interface_exchanged_msgs,

apps/astarte_data_updater_plant/lib/astarte_data_updater_plant/data_updater/queries.ex

@@ -457,6 +457,7 @@ defmodule Astarte.DataUpdaterPlant.DataUpdater.Queries do
 
   defp set_connection_info!(realm, device_id, timestamp, ip_address) do
     keyspace_name = Realm.keyspace_name(realm)
+    timestamp = Ecto.Type.cast!(:utc_datetime_usec, timestamp)
 
     %Device{device_id: device_id}
     |> Ecto.Changeset.change(
@@ -515,6 +516,7 @@ defmodule Astarte.DataUpdaterPlant.DataUpdater.Queries do
         interface_exchanged_bytes
       ) do
     keyspace_name = Realm.keyspace_name(realm)
+    timestamp_ms = Ecto.Type.cast!(:utc_datetime_usec, timestamp_ms)
 
     %Device{device_id: device_id}
     |> Ecto.Changeset.change(