tracking issue - enable rangeproof verifier cache

[antiochp]

• Related tracking issue - invalid rangeproof handling (good header, bad block) #3605
• Related Removing verifier caches #3597

I think we want to do the following initially -

• fix the cache key impl for rangeproofs
  • @jaspervdm suggested implementing DefaultHashable for the full output (identifier + rangeproof)
• revert Removing verifier caches #3597 ensuring we use the correct cache key impl

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Additional possible improvements -

We get most of the benefit from the verifier cache internally in the mempool. We do a lot of tx verification in various mempool operations. For example after aggregating txs together we verify the aggregated tx. Each verification leverages the rangeproof verifier cache as we do not want to verify the rangeproofs repeatedly each time.

But we may want to consider disabling the cache when we actually verify a new block.
Blocks are consensus critical, transactions are not.
We would need to take care to handle edge cases where a potentially invalid tx entered the mempool.
This makes me hesitate a little.

[antiochp]

After some investigation and discussion we are removing the "verifier cache" entirely (for now) -
#3628

Future work may involve reintroducing some form of cache.