hardware_wallet/Ledger `Sign messages` + some refactoring (#8868)

* getting started

* getting started

* signing personal messages works and refactoring

* Refactor `Ledger`

* Make `Ledger Manager` only visible inside the hardwallet-crate
* Refactor `send_apdu` with separate functions for read and write

* Add support for signing messages through `ethcore`

* Trezor modify update_devices and some error msgs

* nits