fix!: return errors from Wallet.peek_address

[reez]

Change Wallet.peek_address to return errors for out of range derivation indexes and descriptors that cannot produce an address (instead of allowing upstream expect() calls to panic)

[Arowolokehinde]

@reez i would like to look into this

[reez]

Wallet.reveal_next_address, next_unused_address, reveal_addresses_to, and list_unused_addresses can reach the same upstream expect("must have address form") as peek_address for bare descriptors, so this issue should cover making all five address returning methods fallible.