Add Swin2SR
# What does this PR do?

Fixes #19568 and replaces #19667 

This PR adds Swin2SR, a Swinv2-based model for image super resolution, compression and restoration.

To do:

- [x] finish `Swin2SRImageProcessor` - should incorporate padding
- [x] fix integration test
- [x] transfer checkpoints to the appropriate organization
_The documentation is not available anymore as the PR was closed or merged._<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.<|||||>Gently pinging @sgugger here