generate op dependency graph as python code
Summary:
Add support to print op dependence as python code so that both custom
build script and BUCK can import it without yaml parser.
Test Plan:
- generate the file:
```
ANALYZE_TORCH=1 FORMAT=py DEPLOY=1 tools/code_analyzer/build.sh -closure=false
```
- load the file in python:
```
python
>>> from tools.code_analyzer.generated.torch import TORCH_DEPS
>>> print(TORCH_DEPS)
```
Differential Revision: D18894639
Pulled By: ljk53
fbshipit-source-id: e304d0525a07a13cf6e8a9317cd22637200d044c
