[Maskformer] Add MaskFormerSwin backbone
# What does this PR do?

This is part 2 of 3 of the big #20204 PR.

This PR adds MaskFormerSwin to the AutoBackbone API. This ensures that the model can be used as backbone with the MaskFormer framework.

As it makes more sense to move MaskFormerSwin to its own modeling files, this PR implements it in a separate `modeling_maskformer_swin.py` file, along with a configuration implemented in` configuration_maskformer_swin.py`.

To do:

- [x] wait for #20407 to be merged to make the backbone get tested by the common tests, add support for hidden states and attentions
_The documentation is not available anymore as the PR was closed or merged._