wallet: BIP 326 sequence based anti-fee-snipe for taproot inputs

The goal of BIP 326 is to provide a "privacy cloak" for txs that use sequence-based locking. This is only possible for taproot inputs, as taproot spends may look identical for "dumb wallets" and "smart contracts" iff they use the key-path spend.

Sequence-based locking has minimally lower anti-fee sniping guarantees if all the txs that created the inputs aren't itself locked to the block they were included in. However, the minimal degradation should be acceptable, given that anti-fee-snipe will set the locktime to the past of 10% of the txs anyway.