#26741: [desktop] Update the project python bootstrap to reset PATH

Make sure applications are launched with the proper DllDirectory set.
I think we should have a try--finally structure here:

```
self._push_dll_state()
try:
    ...
    result = self.execute_hook("hook_app_launch", app_path=app_path, app_args=app_args)
    ...
finally:
    self._pop_dll_state()
```

Just so we can guarantee that the state is preserved even when things error out.