Finalize the documentation of block diffusion pipelining via delayed validation

[amesgen]

Block diffusion pipelining via delayed validation has been implemented in IntersectMBO/ouroboros-network#3688, but the corresponding discussion paper (see IntersectMBO/ouroboros-network#3579) has not been finalized. The goal of this issue is to modify it to accurately describe the already-shipped implementation, comparing it with other internal iterations of the document.

From a cursory glance, it looks like it can mostly stay as it is, excluding the implementation section, which still describes a tentative approach we did not end up using.

Also, it should explain #955

[ghost]

In light of the work currently undertaken by @dnadales and myself on revamping Ouroboros documentation, would it not make sense to turn this document in a markdown file published as part of the consensus docs (eg. https://input-output-hk.github.io/ouroboros-consensus)?

[nfrisby]

Related: https://ouroboros-consensus.cardano.intersectmbo.org/haddocks/ouroboros-consensus/Ouroboros-Consensus-Block-SupportsDiffusionPipelining.html#t:BlockSupportsDiffusionPipelining includes a good high-level explanation