Improve Transaction Validation

In Xline project, it exists the concept of Transaction(hereinafter abbreviated as txn). To keep the atomicity of txn, it need to detect whether all keys within a TxnRequest have overlapping parts. Now, there’s several problems with the Txn Validation function that need to be solved. The order of sub-Txns will affect the result of the entire Txn and Txn Validation's performance is poor. The more important thing is to ensure the correctness of check_intervals fn. But ensuring the correctness will lead to an increase in time complexity, a interval tree is also neccessary to improve Txn Validation's performance.