Use library for Payjoin Sender (#2158)

* Use library for Payjoin Sender

* update payjoin sender to use new package and reduce code

* fix using statements

BTCPayServer/Controllers/WalletsController.cs

@@ -25,6 +25,7 @@ using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Mvc;
 using NBitcoin;
+using BTCPayServer.BIP78.Sender;
 using NBitcoin.DataEncoders;
 using NBXplorer;
 using NBXplorer.DerivationStrategy;