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. 
walInstance->m_last_block_processed_height = *tip_height;
    } else {
        walInstance->m_last_block_processed.SetNull();
        walInstance->m_last_block_processed_height = -1;
    }
    if (tip_height && *tip_height != rescan_height)
    {
        // No need to read and scan block if block was created before
        // our wal birthday (as adjusted for block time variability)
        stdoptional<int64_t> time_first_key;
        for (auto spk_man  walInstance->GetAllScriptPubKeyMans()) {
            int64_t time = spk_man->GetTimeFirstKey();
            if (!time_first_key || time < *time_first_key) time_first_key = time;
        }
        if (time_first_key) {
            FoundBlock found = FoundBlock().height(rescan_height);
            chain.findFirstBlockWithTimeAndHeight(*time_first_key - TIMESTAMP_WINDOW, rescan_height, found);
            if (!found.found) {
                // We were 
                // or a he
                // current 
                rescan_height = *tip_height;
            }
        }
        // Technically we could execute the code below in any case, but performing the
        // `while` loop below can make startup very slow, so only check blocks on disk
        // if necessary.
        if (chain.havePruned() || chain.hasAssumedValidChain()) {
            int block_height = *tip_height;
            while (block_height > 0 && chain.haveBlockOnDisk(block_height - 1) && rescan_height != block_height) {