Apply warm shutdown across coordinators

### Body

Python coordinator implements this in #69034. We should make this also available for other coordinators.

A small-scale refactoring to move the context manager to ActivityProcess so we can do something like:

```python
class ActivitySubprocess:
@classmethod
def run(cls, **kwargs):
with _warm_shutdown_signals():
self = cls.start(**kwargs)
exit_code = self.wait()
return exit_code, self
```

and just use this instead of calling things separately. All coordinators can switch to use this new function. Language side shoould be fine as-is; dedicated signal handling improvements can be made but they are not specific to this.

### Committer

- [x] I acknowledge that I am a maintainer/committer of the Apache Airflow project.