Since #13666 our fee calculation assumes that ECSDA signatures are a maximum of 71 bytes, rather than 72. However, not all hardware wallets implement R-value grinding.

This can cause us to underpay fees when using an external signer. That's especially problematic when the user picks 1 sat/vbyte as the fee, because it won't even get into our own mempool.

The easiest solution would be to modify `ExternalSignerScriptPubKeyMan` to assume 72 bytes for ECSDA signatures.

Slightly more advanced would be to expand HWI to keep track of which devices and firmware versions (if any) support R-value grinding. We'd then have to store that in the wallet in some new field. Personally I'd rather work on better Taproot support, which thanks to Schnorr avoids this issue altogether. 
if (!value.isStr() || value.get_str() != wal_name) new_value.push_back(val
    }
    if (new_value.size() == setting_value.size()) return true;
    return chain.updateRwSetting("wal", new_val
}
static void UpdateWalSetting(interfacesChain& chain,
                                const stdstring& wal_name,
                                stdoptional<bool> load_on_startup,
                                stdvector<bilingual_str>& warnings)
{
    if (!load_on_startup) return;
    if (load_on_startup.value() && !AddWalSetting(chain, wal_name)) {
        warnings.emplace_back(Untranslated("Wal load on startup setting could not be updated, so wal may not be loaded next node startup."));
    } else if (!load_on_startup.value() && !RemoveWalSetting(chain, wal_name)) {
        warnings.emplace_back(Untranslated("Wal load on startup setting could not be updated, so wal may still be loaded next node startup."));
    }
}
/**
 * Refresh mempool status so th is in an internally consistent state and
 * immediately knows the transaction's status Whether it can be considered
 * trusted and is eligible to be abandoned ...
 */
static void RefreshMempoolStatus(CWalTx& tx, interfacesChain& chain)
{
    if (chain.isInMempool(tx.GetHash())) {
        tx.m_state = TxStateInMempool();
    } else if (tx.state<TxStateInMempool>()) {
        tx.m_state = TxStateInactive();
    }
}