BuildCoinbaseMerkleBranch calculate the merkel tree branch for a slice of transactions without coinbase tx.

BuildMerkleTreeStore creates a merkle tree from a slice of transactions, stores it using a linear array, and returns a slice of the backing array.

CalcMerkleTreeRootHash calculate the merkle tree root hash for a slice of transactions.

HashMerkleBranches takes two hashes, treated as the left and right tree nodes, and returns the hash of their concatenation.