CI: add sdist release workflow
- [x] closes #39417


The version that Simon added (temporarily) in #38852 (https://github.com/pandas-dev/pandas/pull/38852/commits/2840c65e94b68ae6eab6bf154a13163a2cb87cef) used a different environment to install the sdist. I think this is important to do here as well? @fangchenli if you have time to update would be good to get this working See also my comment above https://github.com/pandas-dev/pandas/pull/41685#issuecomment-861438693 about Simon's version that uses a separate environment to install the sdist Build sdist without building pandas causes a

```
ModuleNotFoundError: No module named 'pandas._libs.interval'
```

while importing pandas probably not using the installed pandas if /pandas directory still exists from where running the tests thanks @fangchenli 

failures are unrelated (and i think on master) @meeseeksdev backport 1.3.x Something went wrong ... Please have  a look at my logs.