Face cropping based on bounding box still requires facial landmarks / an annotator

Related to #91.

Currently, there is no easy way of cropping the face purely based on bounding boxes, i.e., without alignment based on some facial landmarks. While we have an implementation for this case in FaceCropBoundingBox, but this is buggy, see #91: https://gitlab.idiap.ch/bob/bob.bio.face/-/blob/d6d8e20bb73cfe4b099fedee603fad6498203d7f/src/bob/bio/face/preprocessor/croppers.py#L312 this is not directly called from within out face_crop_sover: https://gitlab.idiap.ch/bob/bob.bio.face/-/blob/d6d8e20bb73cfe4b099fedee603fad6498203d7f/src/bob/bio/face/utils.py#L377 but it is only indirectly included in the BoundingBoxAnnotatorCrop, which uses this only for cutting out the face, and detect landmarks in the crop: https://gitlab.idiap.ch/bob/bob.bio.face/-/blob/d6d8e20bb73cfe4b099fedee603fad6498203d7f/src/bob/bio/face/preprocessor/FaceCrop.py#L305 While this is a useful use-case, another use-case would be to only extract the face based on the bounding box, without further landmark localization and alignment. Actually, in the previous version of Bob, this was possible through (ab-)using the FaceEyesNorm class by providing topleft and bottomright coordinates instead. In the current version, this is no longer possible.

I will add back an option for this.