Test Details Overview

Move wallet types into `nano::wallet` namespace

Extract `fan` and `kdf` classes to separate files in
nano/lib/, add nano/node/wallet/fwd.hpp for forward
declarations, and move all wallet-related types
(`wallet_store`, `wallet`, `wallets`, `wallets_store`,
`mdb_wallets_store`, `wallet_representatives`, `key_type`)
from `nano::` into the `nano::wallet::` namespace.

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Type: commit

Hash: 13cdfc833ead4e57272411153f8d00f66584437b

Created: yesterday

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gr0v1ty/nano-node:13cdfc833ead4e57272411153f8d00f66584437b