Support schema region snapshot parser.

[ColinLeeo]

In this pr:

1. Support translating snapshot file to statements, so you can use schema region snapshot parser to construct a same Schema tree in another cluster.
2. Add some UTs.
3. refine memory use when translating schema region snapshot. The node num depends on the longest path and Its children num. If one path is root.t1.t2.t3, and It has 100 measurements, so the node num will be 4 + 100.