Support custom server in-game nickname

src/main/java/emu/grasscutter/Config.java

@@ -51,6 +51,7 @@ public final class Config {
 	
 	public static class GameServerOptions {
 		public String Name = "Test";
+		public String NickName = "Server";
 		public String Ip = "0.0.0.0";
 		public String PublicIp = "127.0.0.1";
 		public int Port = 22102;

src/main/java/emu/grasscutter/GameConstants.java

@@ -12,6 +12,7 @@ public final class GameConstants {
 	public static final int MAIN_CHARACTER_MALE = 10000005;
 	public static final int MAIN_CHARACTER_FEMALE = 10000007;
 	public static final int SERVER_AVATAR_ID = Grasscutter.getConfig().getGameServerOptions().ServerAvatarId;
+	public static final String SERVER_AVATAR_NAME = Grasscutter.getConfig().getGameServerOptions().NickName;
 	public static final Position START_POSITION = new Position(2747, 194, -1719);
 	
 	public static final int MAX_FRIENDS = 45;

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

@@ -18,7 +18,7 @@ public class PacketGetPlayerFriendListRsp extends BasePacket {
 		
 		FriendBrief serverFriend = FriendBrief.newBuilder()
 				.setUid(GameConstants.SERVER_CONSOLE_UID)
-				.setNickname("Server")
+				.setNickname(GameConstants.SERVER_AVATAR_NAME)
 				.setLevel(1)
 				.setProfilePicture(ProfilePicture.newBuilder().setAvatarId(GameConstants.SERVER_AVATAR_ID))
 				.setWorldLevel(0)