Feature Request: add opt-in bech32 deposit addresses

[cfromknecht]

The current wallet always displays np2wkh addresses to be backwards compatible with existing wallets and exchanges which is great for simplifying the onboarding process.

If a user knows that they will be frequently receiving from a bech32 capable wallet, it would be helpful if users could change the default address type to p2wkh, perhaps via a toggle hidden in the settings interface. This will allow users to take advantage of the fee savings offered by p2wkh addresses and make funding channels cheaper.