Add derivation path selection for ethereum address creation

[joelamouche]

Ethereum address derivation will take one mnemonic and derive a bunch of address with /m/44'/60'/0'/0/0, /m/44'/60'/0'/0/1, etc. We want to allow a user to at least choose the last number in order to derive other address than the zero one. Basically the same UX as address creation in the app

[polkadot-js-bot]

This issue has been open for 21 days with no activity and is not labelled as an enhancement. It will be closed in 7 days.

[joelamouche]

@jacogr Please review