External inputs are currently only supported for initial transaction creation functions. Extend `solving_data` arguments as necessary to support fee bumping wallet transactions with non-wallet inputs.

https://github.com/bitcoin/bitcoin/pull/17211#issuecomment-897653994
#include <string>
#include <utility>
#include <vector>
using interfaces::Chain;
using interfaces::FoundBlock;
using interfaces::Handler;
using interfaces::MakeHandler;
using interfaces::Wallet;
using interfaces::WalletAddress;
using interfaces::WalletBalances;
using interfaces::WalletLoader;
using interfaces::WalletOrderForm;
using interfaces::WalletTx;
using interfaces::WalletTxOut;
using interfaces::WalletTxStatus;
using interfaces::WalletValueMap;
namespace wallet {
namespace {
WalletTx MakeWalletTx(CWallet& wallet, const CWalletTx& wtx)
{
    LOCK(wallet.cs_wallet);
    WalletTx result;
    result.tx = wtx.tx;
    result.txin_is_mine.reserve(wtx.tx->vin.size());
    for (const auto& txin : wtx.tx->vin) {
        result.txin_is_mine.emplace_back(InputIsMine(wallet, txin));
    }
    result.txout_is_mine.reserve(wtx.tx->vout.size());
    result.txout_address.reserve(wtx.tx->vout.size());
    result.txout_address_is_mine.reserve(wtx.tx->vout.size());