VbkBlock finalization check

[Mr-Leshiy]

For VbkBlock need to add some kind of canFinalized() method which will return to us either can we finalize this block or not.

• update VbkBlockAddon, add MerkleTree struct for the VbkPopTxs and fill it with the any new related transaction.
• update VbkBlockAddon, add validation method which will be checked if all possible VbkPopTxs have been already added into the MerkleTree
• update VbkBlockTree, payloads procedure with the filling this new MerkleTree field for the VbkBlockAddond
• update VbkBlockTree finalization procedure with the usage of the new VbkBlockAddond validation method

[Mr-Leshiy]

After a proper discussion with the @Warchant , decide to close this issue, because all these problems will be solved with the final VBK SPV implementation #983