validation, zmq: pass block in UpdatedBlockTip to avoid duplicate read #26375

When CZMQPublishRawBlockNotifier::NotifyBlock is called it calls ReadBlockFromDisk with the passed in block index. However, we will always have already read this block into memory during ActivateBestChain and use it to call BlockConnected. We can check for the tip block there and pass that into UpdatedBlockTip to avoid having the zmq notifier read the block. This also has the benefit of removing the node/blockstorage.h dependency entirely from the zmq code, so we can continue working to remove ReadBlockFromDisk out of global scope (https://github.com/bitcoin/bitcoin/pull/26316#discussion_r1000954807).

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #26308 (rpc/rest/zmq: reduce LOCK(cs_main) scope: ~6 times as many requests per second by andrewtoth)
• #15606 (assumeutxo by jamesob)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

ACK 7b631dc9b1979afc99d9d1a3996492dcb415d3a3 - LGTM

crACK https://github.com/bitcoin/bitcoin/pull/26375/commits/7b631dc9b1979afc99d9d1a3996492dcb415d3a3

This will increase the memory use even if not using zmq. I guess it is fine because the queue is limited?

This will increase the memory use even if not using zmq. I guess it is fine because the queue is limited?

That sounds accurate. It seems LimitValidationInterfaceQueue in the loop prevents this from blowing up.

I don't think this is worth the effort to change anymore. It was a step towards #26316, but I think #26533 is a better way to solve that issue.