Initialize KDF with external wallet

[shamardy]

Currently to connect a wallet like Keplr to KDF / Komodo wallet we need to initialize KDF using an internal passphrase first. It would be beneficial to initialize mm2 in a way that will allow users to connect an external wallet and only use the coins of these wallet. If a coin that needs KDF internal passphrase is to be activated later (e.g. UTXO), then we initialize the internal passphrase at this point.

Related issue that should be fixed with this: #1921
For someone to start working on this issue, this PR #2093 is needed first.