rpcserver+invoicesrpc: alias-aware AddInvoice,AddHoldInvoice rpc

AddInvoice,AddHoldInvoice now issue invoices that include our
peer's aliases. Some extra sanity checks are included to ensure we
don't leak our confirmed SCID for a private channel.

lnrpc/invoicesrpc/invoices_server.go

@@ -331,6 +331,7 @@ func (s *Server) AddHoldInvoice(ctx context.Context,
 		Graph:                 s.cfg.GraphDB,
 		GenInvoiceFeatures:    s.cfg.GenInvoiceFeatures,
 		GenAmpInvoiceFeatures: s.cfg.GenAmpInvoiceFeatures,
+		GetAlias:              s.cfg.GetAlias,
 	}
 
 	hash, err := lntypes.MakeHash(invoice.Hash)