Type coverage for symbolic_convert (#160922)
Summary:
As part of better engineering, we add type coverage to `dynamo/symbolic_convert.py`, which is the main work engine of dynamo for emulating python bytecode.
Running
```
mypy torch/_dynamo/symbolic_convert.py --linecount-report /tmp/coverage_log
```
| -------- | Lines Annotated | Lines Total | % lines covered | Funcs Annotated | Funcs Total | % funcs covered |
| -------- | ------- | -------- | ------- | ------- | ------- | ------- |
| Main | 764 | 4286 | 17.83% | 43 | 241 | 17.84% |
| This PR | 4322 | 4322 | 100.00% | 241 | 241 | 100.00% |
| Delta | +3558 | +36 | +82.17% | +198 | 0 | +82.16% |
X-link: https://github.com/pytorch/pytorch/pull/160922
Approved by: https://github.com/StrongerXi
Reviewed By: seemethere
Differential Revision: D80624982
fbshipit-source-id: 2576111a70925e1322069da2be608f980e51832d
