Add support for Protobuf-based Keyring

[adizere]

Crate

relayer

Summary

We should update Hermes to add support for reading Protobuf-based keyring files.
Many thanks to @colin-axner for help with looking into this.

Problem Definition

Gaia/SDK v0.43+ now generates the key seed file in what they call a "protobuf format".
Relevant issues & PR:
cosmos/cosmos-sdk#7477 -- removes bech32 encoding of pub key (in particular client/keys/add.go)
cosmos/cosmos-sdk#7108
cosmos/cosmos-sdk#9222

If we use a 0.43-based gaiad, then the generated key_seed.json file looks like this:

{"name":"user","type":"local","address":"cosmos1j22jtrmzmhfnjdmppa9ux39z3racypzrj0xv9z","pubkey":"{\"@type\":\"/cosmos.crypto.secp256k1.PubKey\",\"key\":\"Ay0GCrKEf1dla8pjc3ncpHOHkHmwJjaORmAydmjvxy61\"}","mnemonic":"decline clown adult umbrella captain layer pool census neck dilemma stick pink sudden answer bounce forum assist trial royal arch quick flame notice country"}

The relevant field that changed is "pubkey" which contains {\"@type\":\"/cosmos.crypto.secp256k1.PubKey\",\"key....
Previously, the key_seed.json file looked as follows:

{"name":"user","type":"local","address":"cosmos14lu5st469lphc6n2qa9xjm8d7rjj9sf6lrfz3l","pubkey":"cosmospub1addwnpepqvg2584naygs2clsxglt8a4e490dz0qv7evqqkcdthnn5ympfuk62z85lyn","mnemonic":"cushion orbit whisper decide mystery tattoo oval goose piano lesson current nurse wet rhythm record worry bird nothing punch shadow rule bean adult east"}

With the relevant field: "pubkey":"cosmospub1addwnpepqvg2584naygs2clsxglt8a4e490dz0qv7evqqkcdthnn5ympfuk62z85lyn"

If we run the command:

cargo run -q --bin hermes -- -c /Users/adi/.hermes/config.toml keys add ibc-0 -f /Users/adi/Hammers/ibc-rs/data/ibc-0/key_seed.json
Error: cannot generate bech32 account: invalid length

The error can also manifest as:

Error: cannot generate bech32 account: mixed-case strings not allowed

for the input file:

{"name":"user","type":"local","address":"cosmos1gurcj9vwvhxrwk4pknsf4qzqrhqupusnuxd6f8","pubkey":"{\"@type\":\"/cosmos.crypto.secp256k1.PubKey\",\"key\":\"A1+BajmD1O5KcEmQwFJfaZWbpzV2t4Nw29CDEOoxX3UZ\"}","mnemonic":"laptop elegant crater chaos proud number already garbage shadow nerve excuse earn couple build space trip weather twenty burst swift similar region crack bid"}

Acceptance Criteria

These criteria should be further refined, but roughly speaking we'd like to:

• support the new file format
• add an option to convert from the old file format into the newer one, or alternatively make Hermes automatically understand both formats

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