Implement GetOrder for LSPS1

[rolznz]

Currently we just wait until a new channel is created. But it would be better to poll the get_order endpoint to check the state too, for example if the LSP had to refund the payment or for some reason opening the channel is taking longer than expected.

We should also store the LSPS1 order_id in our internal order.

https://github.com/BitcoinAndLightningLayerSpecs/lsp/tree/main/LSPS1#21-lsps1get_order