Rebuild preprocess module and abstract gptmodel class

[Shiduo-zh]

1. rebuild preprocess module into nuplan_rasterize, pdm_vectorize and waymo_preprocess.
2. rebuild TrajectoryGPT model class, and abstract the base model class.
3. add pdm_vectorize preprocess file, but there is still something to do to debug it.
4. add NuplanVectorEncoder class definition, details to be done.
5. rebuild rasterize encoder as multi-choice resnet