Implementing path compression recovery in WOART

[SeKwonLee]

In the current implementation of WOART, we are not providing the implementation for recovering the compressed prefix which can become inconsistent after a crash in the middle of path compression split. Recovering the compressed prefix has two steps; 1) the inconsistent prefix should be identified by comparing the logical and physical depth of tree structure. 2) the correct prefix should be rebuilt by using the inserted key and an existing child. In our current implementation, we are providing the first step, but you can refer to the code lines in our follow-up project (P-ART in RECIPE).