change(consensus) verify that mempool transaction UTXOs are in the best chain

[arya2]

Motivation

The transaction verifier currently checks that spent UTXOs of mempool transactions are in the state queue or on any chain, but it needs to verify that those spent UTXOs are on the best chain so that mined blocks including those transactions will be contextually valid.

Closes #5386

Solution

• Call state service with BestChainUtxo request instead of AwaitUtxo when verifying mempool transactions.
• Add InputNotFound variant to TransactionError for when the spent UTXOs are not present on the best chain.

Review

This PR is part of regular scheduled work.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
• How do you know it works? Does it have tests?

Follow Up Work

• Add a retry_list in the mempool storage for transactions that weren't verified with InputNotFound?

[teor2345]

Thanks, this looks good!

But I think we need to check for unspent outputs, not just any available output. See my detailed note on the request comment.

We might also want to add a TODO to rename AwaitUtxo to AwaitTransactionOutput (the U means "Unspent"). There is already a TODO to combine the Output, Utxo, and OrderedUtxo types, maybe we can add a rename to it as well. But I don't want to do a mass rename during an audit freeze.

[codecov]

Codecov Report

Merging #5616 (ece1be5) into main (beb45fc) will decrease coverage by 0.00%.
The diff coverage is 79.09%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5616      +/-   ##
==========================================
- Coverage   78.75%   78.74%   -0.01%     
==========================================
  Files         305      305              
  Lines       38320    38407      +87     
==========================================
+ Hits        30177    30245      +68     
- Misses       8143     8162      +19     

[teor2345]

Thanks!

I particularly like how you re-used the utxo() function code.