fix: Add Chat-Group-Name-Timestamp header and use it to update group names (#6412)

Add "Chat-Group-Name-Timestamp" message header and use the last-write-wins logic when updating group
names (similar to group member timestamps). Note that if the "Chat-Group-Name-Changed" header is
absent though, we don't add a system message (`MsgGrpNameChangedBy`) because we don't want to blame
anyone.

src/chat.rs

@@ -3039,6 +3039,11 @@ pub(crate) async fn create_send_msg_jobs(context: &Context, msg: &mut Message) -
         msg.state = MessageState::OutDelivered;
         return Ok(Vec::new());
     }
+    if msg.param.get_cmd() == SystemMessage::GroupNameChanged {
+        msg.chat_id
+            .update_timestamp(context, Param::GroupNameTimestamp, msg.timestamp_sort)
+            .await?;
+    }
 
     let rendered_msg = match mimefactory.render(context).await {
         Ok(res) => Ok(res),