ADVZ share duplicates payload data

[ggutoski]

This is bad because it doubles the communication size.

Shares are constructed here:

jellyfish/vid/src/advz.rs

Lines 923 to 932 in 92714a4

	shares.push(Share {
	index,
	evals: mem::take(&mut evals),
	aggregate_proofs: mem::take(&mut proofs),
	evals_proof: all_evals_commit // TODO: check MT lookup for each index
	.lookup(KzgEvalsMerkleTreeIndex::<E, H>::from(index as u64))
	.expect_ok()
	.map_err(vid)?
	.1,
	});

The first copy of payload data is evals, which is what we use everywhere in ADVZ.

The second copy is hidden deep inside evals_proof. The call to lookup returns a MerkleProof, which contains a copy of the payload data as described in #658 .

One of these copies must be eliminated. If we do not remove it from MerkleProof as suggested in #658 then ADVZ should extract the data from there instead of storing an independent copy in Share struct. cc @mrain