[refact] Restructure & clean-up vtkLidarReader
Major changes in vtkLidarReader:
- Hide frame structure internally to avoid fpos errors
- Use an enum to switch between LiDAR time & Network time
- Only reindex frames when necessary
- SaveFrames with network time information
- Change partial frame (first & last) determination
Major vtkLidarInterpreter API changes:
- Rename LoadCalibration to Initialize()
- Simplify PreProcessPacket API signature