[DRAFT] 10x improvement to pop_blocks operation with flag denoting txis are already verified

[0xFFFC0000]

Add already_verified flag to add transaction operation of the txpool. This is very useful when we are popping block, and txis are already verified in that situation, which prevents verifying transactions again.

Numbers on my machine:

popping 500 blocks: master branch ~50 seconds, with this PR ~6 seconds.
popping 2000 blocks: master branch ~210 seconds, with this PR ~29 seconds.

Profiling information of monerod on master branch. As you can see, 80-90% of computation is happening in check_tx_inputs function. The profiling output is attached to this message.

monerod-master-branch-pop_blocks-profile.pdf

[jeffro256]

FWIW, I wrote a similar change in PR #9135: the caller can provide a hard fork version for which it is known that the transaction passes non-input consensus checks. If that is the same version as the version passed into add_tx, then it skips the non-input consensus checks. This is a safer and clearer code path IMO. Also, skipping the input consensus checks is incorrect behavior for txs not kept by block, since a transaction can verify input checks once but then the block reorgs.

[vtnerd]

I would definitely hold off on working too hard on this until @jeffro256 gets his changes in - even if there is additional time savings beyond his PR. He has a pretty big change coming soon.