[ckpt loader] Allow loading the Inpaint and Img2Img pipelines, while loading a ckpt model (#2705)
* [ckpt loader] Allow loading the Inpaint and Img2Img pipelines, while loading a ckpt model
* Address review comment from PR
* PyLint formatting
* Some more pylint fixes, unrelated to our change
* Another pylint fix
* Styling fix