Create a utils command that takes in a wallet.toml and generates the tendermint priv_validator_key.json and node_key.json

[nick-u410]

Tested on: public-testnet-11/12*

Problem:
Currently the only way to generate the priv_validator_key.json deterministically is to namada client utils join-network --chain-id $CHAIN_ID --genesis-validator $ALIAS, this will generate the keys(node_key.json, priv_validator_key.json) from the wallet.toml. However, people who use a remote signer need this key up front on their remote signer machine. Validators would prefer a way to get these keys before joining the network.

Potential Solution:
Create a utils command that takes in a wallet.toml and generates the tendermint priv_validator_key.json and node_key.json

[sug0]

Duplicate of #1155