Adding key generation algorithm for "eth_secp256k1"

[leejw51crypto]

currently, we can generate keys like this, default algo is secp256k1

hermes keys restore ethermint-2  -m "my mnemocnis.." -t 60

that's different from ethermint's one.

ethermintd keys add $KEY --keyring-backend test --algo "eth_secp256k1"

so we can add like this

hermes keys restore ethermint-2  -m "my mnemocnis.." -t 60 --algo "eth_secp256k1"

so user can freely designate 20 payload address representaion algorithm.

for example

secp256k1:   pubkey->sha256->last 20 bytes
eth_secp256k1: pubkey->sha256->ripemd160->20 bytes

also we can support other cosmos network which uses different address logic.

[adizere]

This seems related to #1155.

@leejw51crypto we plan to get to this by end of October. Please let us know if that timeline is OK, or if you have more specific time constraints in mind.

[xlab]

We at InjectiveLabs also run Ethermint-compatible chain, implemented full support for the eth_secp256k1 keys here
InjectiveLabs@28e7c65

[devashishdxt]

@xlab How do you handle 2nd point in #1267?

[xlab]

@devashishdxt I just got up to the 2nd point. Debugging to see what's wrong there on the ibc-rs side.