P-Chain staking to a new address

[aphexmunky]

Given the recent interest in quantum resistance, it might be beneficial to introduce an address where the original P-chain stake amount should move to either prior or at the point of unlock. We have this concept in stake rewards and delegation fees but the base amount doesn't move.

Core wallet is reusing the P-chain addresses unless very intentionally moving them and with the current max stake period being a year, it makes sense to tackle this before or as part of continuous staking if that's still in the roadmap