Function fake_orchard_bundle_duplicate_nullifiers 

pub fn fake_orchard_bundle_duplicate_nullifiers(
    flags: Flags,
    value_balance: ZatBalance,
    n_actions: usize,
    seed: u64,
    bundle_version: BundleVersion,
) -> Bundle<Authorized, ZatBalance>

Builds an Orchard-shaped bundle whose actions all share a single nullifier.

Used by duplicate-nullifier consensus tests, which need a within-transaction double spend.