Compute receipts root

[MegaRedHand]

We need to compute the Merkle Patricia Tree's root for the receipts generated after executing all the transactions in a given block body. For an example, see the computation for the transactions root:

ethrex/crates/core/src/types/block.rs

Lines 80 to 111 in 49f0374

	pub fn compute_transactions_root(&self) -> H256 {
	let transactions_iter: Vec<_> = self
	.transactions
	.iter()
	.enumerate()
	.map(|(i, tx)| {
	// TODO: check if tree is RLP encoding the value
	// Key: RLP(tx_index)
	let mut k = Vec::new();
	i.encode(&mut k);
	// Value: tx_type || RLP(tx) if tx_type != 0
	// RLP(tx) else
	let mut v = Vec::new();
	match tx {
	// Legacy transactions don't have a prefix
	Transaction::LegacyTransaction(_) => {}
	_ => v.push(tx.tx_type()),
	}
	tx.encode(&mut v);
	(k, v)
	})
	.collect();
	let root = PatriciaMerkleTree::<_, _, Keccak256>::compute_hash_from_sorted_iter(
	&transactions_iter,
	);
	H256(root.into())
	}
	}

You can check how values are encoded in Ethereum's yellow paper. Similar to transactions, the key should be computed as KECCAK256(RLP(receipts_index)) and the value as tx_type (if tx_type != 0) || RLP(receipt).