owlvit/2 dynamic input resolution (huggingface#34764)

* owlvit/2 dynamic input resolution.

* adapt box grid to patch_dim_h patch_dim_w

* fix ci

* clarify variable naming

* clarify variable naming..

* compute box_bias dynamically inside box_predictor

* change style part of code

* [run-slow] owlvit, owlv2

Author: bastrob