Improvements and send all mail fix

Mail ID no longer exists and is handled by it's position in the mail array

src/main/java/emu/grasscutter/server/packet/send/PacketMailChangeNotify.java

@@ -46,7 +46,7 @@ public class PacketMailChangeNotify extends GenshinPacket {
                 }
 
                 MailDataOuterClass.MailData.Builder mailData = MailDataOuterClass.MailData.newBuilder();
-                mailData.setMailId(message._id);
+                mailData.setMailId(player.getMailId(message));
                 mailData.setMailTextContent(mailTextContent.build());
                 mailData.addAllItemList(mailItems);
                 mailData.setSendTime((int) message.sendTime);