fix: update merkle tree

[matteo-cristino]

• added a function for test vectors in merkle_tree.lua, created tests for creation merkle tree check_merkle_tree.lua
• chore(style): remove trailing whitespaces

[jaromil]

very well, there is no fix: commit so I'll wait for merge in case we want to trigger release

[matteo-cristino]

TODO:

• ✅ add merkle vector test to run with all other test (add it to bats file in vector test)
• ✅ vector tests do not work beacuse function called are local in zencode_merkletree.lua, maybe create crypto_merkletree.lua as we did for the other packages?
• ✅ vector test call a non existing data2 dictioanry

[matteo-cristino]

✅ bonus point: maybe _create_merkle_tree can be optimized, I'm not sure if the first for loop where all the tree is set to 0 string is really needed 🔮