Change way we retrieve information from library

[Saleciani]

On BDK flutter methods are no longer "Future"

  /// Return the list of transactions made and received by the wallet. Note that this method only operate on the internal database, which first needs to be [Wallet.sync] manually.
  @override
  List<TransactionDetails> listTransactions({required bool includeRaw, hint}) {
    try {
      return super
          .listTransactions(includeRaw: includeRaw)
          .map(
            (e) => TransactionDetails._(
              transaction: e.transaction,
              txid: e.txid,
              received: e.received,
              sent: e.sent,
              fee: e.fee,
              confirmationTime: e.confirmationTime,
            ),
          )
          .toList();
    } on BdkError catch (e) {
      throw mapBdkError(e);
    }
  }

where is LWK

  /// Get the transaction history of the wallet
  Future<List<Tx>> txs() => LwkCore.instance.api.crateApiWalletWalletTxs(
        that: this,
      );

It would be much better to have (most) of the methods from the wallet not as futures.

This would improve the way users of the Library can build wallets, not depending on async behavior, and it would better match BDK