draft: Validator eth secp keys

[tzemanovic]

depends on #254 and #318

This PR adds 2 required validator eth bridge secp256k1 keys - hot and cold. Hot key will be used for signing validator set updates and cross-chain transactions (done by the ledger) and cold key for bridge governance (done on-demand by validators).

to-do:

• add fn to derive Eth address from secp256k1 address (or use some crate)
• Add a PoS storage map from eth address to namada address and set the associations when we write eth cold and hot keys
• update PoS VP to check eth keys
• update Pos VP test

[sug0]

note:

fn read_validator_eth_hot_key(
    &self,
    key: &Self::Address
) -> Option<Self::PublicKey>

this method should return Option<ValidatorEthKey<Self::PublicKey>> instead; same for write_validator_eth_hot_key, but in that case, we invert the order of inputs and outputs

---

EDIT: solved here 0ef4072

[tzemanovic]

this is going to stay in draft for now - it's only partially finished, because some updates depend on other PoS changes that are not in eth-bridge-integration yet, but it unblocked the bridge dev itself

[cwgoes]

@batconjurer @tzemanovic Is this PR still relevant? Should it be merged into the Ethereum bridge integration branch, perhaps?

[sug0]

@cwgoes it's already in eth-bridge-integration, but not in main, due to missing some VPs, still

[adrianbrink]

Closing this since it's stale. If we need commits from this then @batconjurer @sug0 can pick them into a new PR.