Remove Byron Bech32 support

[newhoggy]

We use the prefix to distinguish keys, but according to the code, Byron and Shelley share the same prefix:

instance SerialiseAsBech32 (VerificationKey ByronKey) where
    bech32PrefixFor         _ =  "addr_xvk"
    bech32PrefixesPermitted _ = ["addr_xvk"]

instance SerialiseAsBech32 (VerificationKey PaymentExtendedKey) where
    bech32PrefixFor         _ =  "addr_xvk"
    bech32PrefixesPermitted _ = ["addr_xvk"]

We use the following list when deserialising:

    bech32Types =
      [ FromSomeType (AsVerificationKey AsByronKey)
                     AByronVerificationKey
      , FromSomeType (AsVerificationKey AsPaymentKey)
                     APaymentVerificationKey
      , FromSomeType (AsVerificationKey AsPaymentExtendedKey)
                     APaymentExtendedVerificationKey
      ]

So when deserialising a key like addr_xvk18359zklg0x68ru6yhxyvsv3slt6wscs00mzsc45jrv9840dfutj5uxg6z6rp4w2pany4kjgg5tly8s5xv7fuyq5tf8kw9ehr7cy4lzcenyhck, it thinks the keys are Byron because Byron appears first in the list and shares the same prefix as Shelley.

Having an instance for Byron declare that Byron keys have the addr_xvk prefix seems wrong. This PR removes support for serialising and deserialising Byron keys with that prefix.

[newhoggy]

This fixes #2596

With this change the following works as expected:

$ cardano-cli address build --payment-verification-key addr_xvk18359zklg0x68ru6yhxyvsv3slt6wscs00mzsc45jrv9840dfutj5uxg6z6rp4w2pany4kjgg5tly8s5xv7fuyq5tf8kw9ehr7cy4lzcenyhck --testnet-magic 1097911063
addr_test1vptgn6nxuhfc0rt3s7xydxlczm2rncn7dhcqt4jp4d9edqqax2mf6%
$ cardano-cli address info --address addr_test1vptgn6nxuhfc0rt3s7xydxlczm2rncn7dhcqt4jp4d9edqqax2mf6

[dcoutts]

So now the only way to use Byron keys is via a file (using text envelope format) right?

[newhoggy]

So now the only way to use Byron keys is via a file (using text envelope format) right?

Yep.

[newhoggy]

bors merge

[iohk-bors]

Build succeeded:

• ci/hydra-eval
• buildkite/cardano-node
• ci/hydra-build:required