Fix RT-DETR inference with float16 and bfloat16 (#31639)
* [run_slow] rt_detr
* Fix positional embeddings and anchors dtypes
* [run slow] rt_detr
* Apply suggestions from code review
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>
* Fixup
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Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>