Send looked up UTXOs to the transaction verifier

[teor2345]

Motivation

We need to calculate the transaction fee to implement ZIP-401.
We need to get the UTXOs to calculate the values of transparent inputs.

Consensus Rules

low_fee_penalty is 16000 if the transaction pays a fee less than the conventional fee, otherwise 0

https://zips.z.cash/zip-0401#specification

Solution

• Return the spent outpoint and UTXO in the script verifier response
• Send the UTXOs from each response to the main transaction verifier future
• Collect those UTXOs into a HashMap
• Add some temporary errors and assertions to check that the code works (they will be replaced by the tests in tickets Reject duplicate UTXO spends and nullifier reveals within the same mempool transaction #2787 and Return the transaction fee in the mempool response #2779)

Closes #2440

Review

@upbqdn needs this for ticket #2779.
@oxarbitrage might be interested as well.

Reviewer Checklist

• Code implements Specs and Designs
• Tests for Expected Behaviour
• Tests for Errors

Follow Up Work

Use these UTXOs to calculate the transaction fee #2779
Replace the temporary double-spend error with the actual check #2787

[upbqdn]

I actually reviewed all the code today and it looks good to me.

[teor2345]

This change shouldn't conflict with any open PRs, so I've set it to auto-merge.

[dconnolly]

👍