Add table transformer [v2] (#19614)
* First draft
* Add conversion script
* Make conversion work
* Upload checkpoints
* Add final fixes
* Revert changes of conditional and deformable detr
* Fix toctree, add and remove copied from
* Use model type
* Improve docs
* Improve code example
* Update copies
* Add copied formt
* Don't update conditional detr
* Don't update deformable detr