[FEATURE] Allow users to have addresses in config.terrain.json

[emidev98]

Describe the feature

Create new field on config.terrain.json that allow the user to setup mnemonics or private keys.

Describe the solution you'd like

The config.terrain.json could look like:

{
    ...,
    "wallets" : {
        "[mnemonicName]": {
            "mnemonic": "...",
        },
        "[privateKeyName]": {
            "privateKey": "...",
        }
    },
    ....
}

Where [mnemonicName] or [privateKeyName] can be the value for **--signer ** parameter when a user has to sign a TX