Add helper for circular rebalancing

[tnull]

We had users interested in circular rebalancing. Of course, selecting two channels (send/receive over) to use, crafting an appropriate path and sending a spontaneous payment should be rather trivial to achieve with LDK's current API, but it would still be nice to have a convenient helper method for it, similar as we do for payment probing.

[valentinewallace]

May be a duplicate of #2462

[tnull]

May be a duplicate of #2462

Yeah, that might be a prereq, but I think this issue is slightly different, as it's about providing convenience helpers to create a circular route mostly.

[Oochenn]

hi can I take this ?

[tnull]

hi can I take this ?

Yes, although we might need #2462 first, as discussed above. Would you also be interested in picking that up?

[Oochenn]

yes sure 🙂