Wallet: Clean up unused state / refactor BTC part

[gbarkhatov]

We are using some state that can be removed

  const [btcWalletProvider, setBTCWalletProvider] =
    useState<IBTCWalletProvider>();
  const [network, setNetwork] = useState<networks.Network>();
  const [publicKeyNoCoord, setPublicKeyNoCoord] = useState("");
  const [address, setAddress] = useState("");