Config and Registry: create a separate buck target

Summary:
Pull Request resolved: https://github.com/facebookresearch/d2go/pull/546

Here we start modularizing the targets. I had to introduce some temporary hacks to break the circular dependency while keeping the diff atomic. There are some TODOs left at the end of the stack that are still WIP.

Reviewed By: tglik

Differential Revision: D45912076

fbshipit-source-id: 375f579fe749dd4a588908cdca7b76ba68f1048f

d2go/utils/misc.py

@@ -8,7 +8,6 @@ import warnings
 from contextlib import contextmanager
 from typing import Any, Callable, Dict, Iterator, Optional
 
-# @manual=//vision/fair/detectron2/detectron2:detectron2
 import detectron2.utils.comm as comm
 import torch
 from d2go.config import CfgNode