move the BBN staking logic into a better place

[jrwbabylonlab]

We’ve temporarily kept the entire staking creation logic within simple-staking for easier debugging and faster updates during rapid development iterations.

We should consider abstracting this complex logic (delegation creation, EOI, etc.) into a separate library so that simple-staking can focus on its UI representation rather than the staking logic itself. Part of the investigation for this ticket will determine whether a new library is needed or if it should be incorporated into btc-staking-ts.