[WIP] Add SPTSv2
# What does this PR do?

This PR adds SPTSv2. Per the docs, I am opening this PR immediately after generating the boilerplate.

Fixes #24235


cc @alaradirik for information. Please let us know when your model is ready for review or if you need any help :-)<|||||>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.