fix: Fix emitting ContactsChanged events on "recently seen" status change (#5377)

- Always emit `ContactsChanged` from `contact::update_last_seen()` if a contact was seen recently
  just for simplicity and symmetry with `RecentlySeenLoop::run()` which also may emit several events
  for single contact.
- Fix sleep time calculation in `RecentlySeenLoop::run()` -- `now` must be updated on every
  iteration, before the initial value was used every time which led to progressively long sleeps.

src/test_utils.rs

@@ -1100,7 +1100,10 @@ fn print_event(event: &Event) {
                 "Received MSGS_CHANGED(chat_id={chat_id}, msg_id={msg_id})",
             ))
         ),
-        EventType::ContactsChanged(_) => format!("{}", green.paint("Received CONTACTS_CHANGED()")),
+        EventType::ContactsChanged(contact) => format!(
+            "{}",
+            green.paint(format!("Received CONTACTS_CHANGED(contact={contact:?})"))
+        ),
         EventType::LocationChanged(contact) => format!(
             "{}",
             green.paint(format!("Received LOCATION_CHANGED(contact={contact:?})"))