Add static version of regular merkle root calculation

[shuse2]

Description

Add below function to the regular merkle tree and expose from index.ts

calculateMerkleRootWithLeafs(leafData: Buffer[]): Buffer

Motivation

Currently regular merkle tree class is used for both one time merkle root calculation and consecutive merkle root calculation. However, this function must be async to support saving the merkle tree data into database.
We want to calculate the merkle root in synchronous function in case of creating transaction root and asset root.

Acceptance criteria

• Function is unit tested against the fixture