Depends on D11886
As per T2599, this is part of a stacked diff to sign utxos for non-eToken txs by matching wit to address.
This diff:
- adds a getUtxoWif helper function to extract the WIF for a given UTXO
- changes the cashtab messaging decryption logic to use getUtxosWif to obtain the funding wif rather than relying on the soon to be deprecated .wif attribute of an XEC utxo object