feat: add validation time to block proposal response

[obycode]

Fixes #5464

[hstove]

This LGTM, but my question is - what exactly do we want to compute as the "computation time"? In this case we have some checks around the block's payload, checks around valid tenure/parent, etc. Is there anything in there that's not relevant to what we care about?

My guess is that it's all stuff we care about, but just asking the question.

[obycode]

This LGTM, but my question is - what exactly do we want to compute as the "computation time"? In this case we have some checks around the block's payload, checks around valid tenure/parent, etc. Is there anything in there that's not relevant to what we care about?

My guess is that it's all stuff we care about, but just asking the question.

That's a good question. We basically are trying to get some estimate of the time it will take a node to process this block if it were broadcast as a real block. These same kinds of checks happen there, e.g. in process_next_nakamoto_block, so I think it is correct that we capture all of that. I don't think there is an exact 1:1 mapping, but it should be a reasonable estimate.