feat: ensure that both the account and public key get inserted successfully in the CLI

[tomyrd]

In #718 we separated the secret key storage from the Client. The CLI now has the responsibility of adding new keys to the keystore, but there could be a case where the key is inserted but the new account can be added to the client.

This is fine for now but maybe we could add a TODO here to address potential cases where adding the secret key succeeds, but adding the account fails.

Alternatively, maybe in the future we want to have some sort of "keystore" command that adds/removes keys separately from accounts.

Originally posted by @igamigo in #718 (comment)