DRAFT: feat(chain): check remaining blocks in IBD to enable blob validation

[youngjoon-lee]

1. What does this PR implement?

Partially resolves #1675.

We starts IBD with disabling blob validation.
At some point during IBD, we should enable the blob validation.
For now, we agreed on enabling it once entering the DA window (which is not defined yet).
So, this PR defines a parameter ibd.last_blocks_with_blob_validation. If there are remaining blocks to the target less than the parameter, IBD enables blob validation.

This PR doesn't yet use the historical blob sampling API after enabling blob validation. Still it skips blob validation. I will change it once all other components (services) are ready. This PR just prepares the foundation.

Also, I promise I will open a refactoring PR soon to prevent making the chain service more verbose. I have an idea, but didn't want to make this PR hard to review.

2. Does the code have enough context to be clearly understood?

yes

3. Who are the specification authors and who is accountable for this PR?

@youngjoon-lee

4. Is the specification accurate and complete?

yes

5. Does the implementation introduce changes in the specification?

no

Checklist

Warning

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• 1. The PR title follows the Conventional Commits specification.
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[zeegomo]

Not against this, but it's not critical so if we don't know yet how it will be used or have other reasons to postpone it (e.g. it will become clearer after other things have been finished) then it's perfectly fine to put it on hold

[zeegomo]

how should we interpret this value and how would one select it?

[youngjoon-lee]

This value must be defined in the DA spec, because this means the period how long DA nodes will keep blobs. But, it is not determined yet. I added this parameter here because we anyway need to for IBD.

[zeegomo]

shouldn't this be first block with validation?

[youngjoon-lee]

I intended this parameter to represent the number of "remaining" blocks. So, I think that "last" makes more sense.

If there are N blocks in total that we have to catch up during IBD, and if there are last_blocks = 8000,
we're going to disable blob validation while we process N - 8000 blocks. After that, we will enable blob validation for next 8000 blocks.

Please let me know if this naming doesn't sound good. I will try to think about other names (or updating comments).