refactor(utxo-lib): extend verifySignature test
refactor(utxo-lib): extend verifySignature test

We have an implicit test in `integration_local_rpc` but it is worth
having a more thorough dedicated one.

Issue: BG-34381

BitGo/BitGoJS,BitGo/BitGoJS,BitGo/BitGoJS,BitGo/BitGoJS