Update blob_sidecar type

[EchoAlice]

Fixes #306.

Note: kzg_commitment_inclusion_proof is a vector of Bytes32 in python spec.
Do we want it to be an array?

pub kzg_commitment_inclusion_proof = [Bytes32; KZG_COMMITMENT_INCLUSION_PROOF_DEPTH]

[ralexstokes]

the inclusion proof is a SSZ Vector

copying here:

class BlobSidecar(Container):
    index: BlobIndex  # Index of blob in block
    blob: Blob
    kzg_commitment: KZGCommitment
    kzg_proof: KZGProof  # Allows for quick verification of kzg_commitment
    signed_block_header: SignedBeaconBlockHeader
    kzg_commitment_inclusion_proof: Vector[Bytes32, KZG_COMMITMENT_INCLUSION_PROOF_DEPTH]

It's important for the SSZ serialization and hash tree root that the types match exactly.

So you can just import Vector from the ssz prelude: use crate::ssz::prelude::Vector along w/ the Bytes32 type if you need it

[ralexstokes]

nice! we can drop the signed envelope but then this looks g2g

[ralexstokes]

looks great! Nice work :)