lnrpc+rpcserver: thread GenAmpInvoiceFeatures to invoicesrpc

lnrpc/invoicesrpc/config_active.go

@@ -55,4 +55,8 @@ type Config struct {
 	// GenInvoiceFeatures returns a feature containing feature bits that
 	// should be advertised on freshly generated invoices.
 	GenInvoiceFeatures func() *lnwire.FeatureVector
+
+	// GenAmpInvoiceFeatures returns a feature containing feature bits that
+	// should be advertised on freshly generated AMP invoices.
+	GenAmpInvoiceFeatures func() *lnwire.FeatureVector
 }