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. 
* block locator and m_last_block_processed, and registering for
     * notifications about new blocks and transactions.
     */
    static bool AttachChain(const std::shared_ptr<CWallet>& wallet, interfaces::Chain& chain, const bool rescan_required, bilingual_str& error, std::vector<bilingual_str>& warnings);
    static NodeClock::time_point GetDefaultNextResend();
public:
    /**
     * Main wallet lock.
     * This lock protects all the fields added by CWallet.
     */
    mutable RecursiveMutex cs_wallet;
    WalletDatabase& GetDatabase() const override
    {
        assert(static_cast<bool>(m_database));
        return *m_database;
    }
    /** Get a name for this wallet for logging/debugging purposes.
     */
    const std::string& GetName() const { return m_name; }
    typedef std::map<unsigned int, CMasterKey> MasterKeyMap;
    MasterKeyMap mapMasterKeys;
    unsigned int nMasterKeyMaxID = 0;
    
    CWallet(interfaces::Chain* chain, const std::string& name, std::unique_ptr<WalletDatabase> database)
        : m_chain(chain),
          m_name(name),
          m_database(std::move(database))
    {
    }
    ~CWallet()