PHOENIX-4925 Use a Variant Segment tree to organize Guide Post Info

[binshi-bing]

@dbwong please review this early draft. Haven't completely sorted out local index and cross region boundary condition when generating scan. Still adding unit test and integration test and trying to pass the tests. Please focus on main logic, data structure, main algorithms and interfaces first. The main data structure change is in GuidePostsInfo for now.

[karanmehta93]

@BinShi-SecularBird can you fix the conflicts?

[binshi-bing]

@dbwong , could you please review BaseResultIterators.getParallelScans()? All the required changes should be there now. BaseResultIterators.getRowKeyRanges() contains the logic of generating query key ranges for local index.