keys: supporting different keyring backends

Cosmos SDK has different types of [keyring backends](https://github.com/cosmos/cosmos-sdk/blob/v0.46.4/crypto/keyring/keyring.go#L29-L37): `file`, `os`, `kwallet`, `pass`, `test`, and `memory`. The current codebase (and also lensclient) only support `test`. Would be good if we extend the client to support all of them.