Split verification failures by match type and rejection expiry

[teor2345]

Motivation

When the mempool fails to verify transactions, it caches those verification failures.

Match Type

If the failure is due to the transaction's effects (for example, a double-spend), any transaction with the same TXID (Hash) is also invalid.

If the failure is due to the authorizing data (for example, a bad signature), only that exact WTXID (UnminedTxId) is invalid.

In #2819, we did an initial split of the non-transaction::Verifier errors.

Rejection Expiry

Some failures persist until a rollback (for example, Expired).
Others should only be cached until the next block is committed (for example, SpendConflict).

We could split transaction::Verifier errors into these categories.

In #2694, we did an initial split of the non-transaction::Verifier errors.

Priority

This ticket is not required for a minimal mempool implementation.

zcashd implements a similar solution, but some of their engineers say they could do better:

• Match rejected transactions correctly by TXID or WTXID #2819 (comment)
• Match rejected transactions correctly by TXID or WTXID #2819 (comment)

Specifications

These mempool consensus rules are currently unspecified.

[teor2345]

This is either obsolete or not needed.