Use `deformable_detr` kernel from the Hub (#36853)
* Use `deformable_detr` kernel from the Hub
Remove the `deformable_detr` kernel from `kernels/` and use the
pre-built kernel from the Hub instead.
* Add license header
* Add `kernels` as an extra `hub-kernels`
Also add it to `testing`, so that the kernel replacement gets tested
when using CUDA in CI.
