--app:
1. Add optimizer checkpoint and training resumption support.
2. Add better tensorboard support.
3. Add nerf distortion loss.
4. Support multi-focal in city dataloader.

--dist_render:
1. Support dynamic fetching, a strategy to prefetch and offload parameters for limited GPU memory, to support infinite rendering area.

Bugfix:
1. Fix augments shadow copy bug
2. Delete deprecated dataloader in dist_render
3. Refactor the import way in different modules