tree hash for blobs bundle

[ltitanb]

Issue Addressed

ref: #7367

Proposed Changes

Implement TreeHash for BlobsBundle

[jimmygchen]

I don't believe this is required - please provide rationale if you think otherwise - happy to re-open.

[jimmygchen]

Hi @ltitanb

Sorry for closing this abruptly without details - I'd like to add more info here - in the CL we don't expect to hash this object, that's why this wasn't implemented.

In PeerDAS/Fulu, we've updated the length of VariableList without introducing a new version, hence the hash produced would be different to before. If we need tree hashing on this object, then we'd need to introduce a new BlobsBundle version for PeerDAS, which requires a bit more boilerplate.

[jimmygchen]

See

lighthouse/consensus/types/src/lib.rs

Lines 275 to 282 in 759b061

	// Note on List limit:
	// - Deneb to Electra: `MaxBlobCommitmentsPerBlock`
	// - Fulu: `MaxCellsPerBlock`
	// We choose to use a single type (with the larger value from Fulu as `N`) instead of having to
	// introduce a new type for Fulu. This is to avoid messy conversions and having to add extra types
	// with no gains - as `N` does not impact serialisation at all, and only affects merkleization,
	// which we don't current do on `KzgProofs` anyway.
	pub type KzgProofs<E> = VariableList<KzgProof, <E as EthSpec>::MaxCellsPerBlock>;

[ltitanb]

Noted, thanks for the explanation!