Accept CashAddr prefixes in bitcoin-tx input
bitcoin-tx accepts CashAddr addresses as input, but errors if the
address includes an explicit prefix (i.e. bitcoincash:
, bchtest:
, or
bchreg:
). This fixes the error.
This deals with bitcoin-tx input, while !274 (merged) deals with bitcoin-tx output. Merge either this or !274 (merged), and I'll rebase the other one.
Test plan: ninja check
(this includes the bitcoin-tx
tests)