Annoying attack on segwit transactions

Attack:
https://blog.trezor.io/details-of-firmware-updates-for-trezor-one-version-1-9-1-and-trezor-model-t-version-2-3-1-1eba8f60f2dd

We need to either show `fee:unknown` if `non_witness_utxo` is not present in PSBT, or store tx history and show a warning if we see the same txid with a different amount.

If `non_witness_utxo` is present we need to check it and optionally convert it to `witness_utxo` for signing.

PSBT implementation was ignoring `non_witness_utxo` because we didn't support legacy transactions. Now we need to add support for them and also properly sign witness transactions when `non_witness_utxo` is provided.