BIP-352: scanning: add step to skip tx if input pubkeys sum A is point at infinity

The input data for the test vector is taken from the signet transaction
fe788cf6578d547819def43d79e6c8f0153d4885f5a343d12bd03f34507aabd6
which spends two P2WPKH inputs with negated pubkeys (x, y) and (x, -y)
from the funding transaction 3a286147b25e16ae80aff406f2673c6e565418c40f45c071245cdebc8a94174e
(see also https://github.com/bitcoin-core/secp256k1/pull/1519#issuecomment-2143167510
and the output from the script in the previous commit message).

Co-authored-by: josibake <josibake@protonmail.com>

bip-0352/reference.py

@@ -300,6 +300,10 @@ if __name__ == "__main__":
             add_to_wallet = []
             if (len(input_pub_keys) > 0):
                 A_sum = reduce(lambda x, y: x + y, input_pub_keys)
+                if A_sum.get_bytes() is None:
+                    # Input pubkeys sum is point at infinity -> skip tx
+                    assert expected["outputs"] == []
+                    continue
                 input_hash = get_input_hash([vin.outpoint for vin in vins], A_sum)
                 pre_computed_labels = {
                     (generate_label(b_scan, label) * G).get_bytes(False).hex(): generate_label(b_scan, label).hex()