feat: allow `cast wallet` to register Ledger/other HW wallets

### Component

Cast

### Describe the feature you would like

It would be a QoL improvement to be able to add/register a Ledger wallet with a mnemonic index with `cast wallet`, so that it could then be used with `forge script --account`.

Reasoning:
- It saves the user from having to remember the mnemonic index
- `cast wallet` can cache the public key of the wallet
- When #10632 is implemented, it would also save the user from having to specify the `--sender` flag, since it's cached/can be determined

### Additional context

_No response_