zpay32: add functional opt to error out on unknown feature bit

This commit adds two functional options to the zpay32.Decode function.
`WithKnownFeatureBits` allows the caller to overwrite the default set of
known feature bits used by the function.
`WithErrorOnUnknownFeatureBit` allows the caller to instruct the
function to error out if the invoice that is decoded contaijns unknown
feature bits. We then use this new error-out option from the
`rpcServer`'s `extractPaymentIntent` method.

rpcserver.go

@@ -5210,6 +5210,7 @@ func (r *rpcServer) extractPaymentIntent(rpcPayReq *rpcPaymentRequest) (rpcPayme
 	if rpcPayReq.PaymentRequest != "" {
 		payReq, err := zpay32.Decode(
 			rpcPayReq.PaymentRequest, r.cfg.ActiveNetParams.Params,
+			zpay32.WithErrorOnUnknownFeatureBit(),
 		)
 		if err != nil {
 			return payIntent, err