LSPS2: Allow selecting LSP based on node id

[JssDWt]

In the LSPS2 context, it would make sense if you could select a LSP, even if it's not returned by lsp_list in the Breez api, as long as it supports LSPS2. Requires migration of the selected LSP. It makes sense to make the LSP id equivalent to the LSP node id.