Allow small machines to create transactions

[Sword-Smith]

This logic in create_transaction_from_data_worker is expensive to execute:

let proof = TransactionProof::ProofCollection(ProofCollection::produce(&primitive_witness));

Adding a path through this code where only the lock script satisfaction is proven will allow weak machines to initiate (non-privacy-preserving) transactions. Let's add an Incomplete variant to ProofCollection that is used when only the lock scripts are proven.