Fix _CudaStreamBase type annotations (#111387)
Make it inherit from `Stream` as indeed it is, see https://github.com/pytorch/pytorch/blob/97a513ed077323550b808e690a0b5a0452f87334/torch/csrc/cuda/Stream.cpp#L208 and
```
python3 -c "import torch;print(torch._C._CudaStreamBase.__base__)"
<class 'torch.Stream'>
```
Fixes https://github.com/pytorch/pytorch/issues/111268
TODO (in separate PR): Revive `test_typing` and add regression test
Pull Request resolved: https://github.com/pytorch/pytorch/pull/111387
Approved by: https://github.com/jeanschmidt, https://github.com/Skylion007
