deneb: Suggest sidecars by root callers verify blob sidecars

[ralexstokes]

Suggest readers of BlobSidecarsByRoot also verify KZG proofs of blob data.

[ppopth]

Looks good to me

[djrtwo]

@jtraglia was wondering why this wasn't explicitly there but was in the byRange request

I believe it's not explicitly here because you always have the block when doing this byRoot request. So you can put each message that comes in, into whatever validation workflow you want in relation to the block as you pull them down

Whereas in byRange, you might be syncing blocks and sidecars at the same time and not necessarily have the related block so there is an explicit SHOULD because you can't for-sure do it.

That said -- It's fine to put that in here explicitly to just point out to the reader that this isn't a bad option as an early validation to know if you're dealing with a correct peer or not