feat: a convenience method for transferring all the balance to another address

[deefactorial]

Feature Request:
A convenience method for transferring all of the balance of one address to another address.

Currently, you have to specify the amount you want to transfer, and you can't transfer the whole exact amount because you need to allow for transaction fees. It would be convenient if there was a method to transfer the whole balance of one account to another account. This would also reduce the number of accounts left with residual balances.

For example pow wallet send t1address t2address all.