Add cutmix generator

[gosha20777]

Add cutmix generator for beter results.
The cutmix generator can be useful for training models and achieving better results. This will help take existing models to a higher level of quality.

Resources that may be useful:

• https://arxiv.org/abs/1905.04899 - the original article
• https://github.com/clovaai/CutMix-PyTorch - a pytorch implementation
• https://github.com/DevBruce/CutMixImageDataGenerator_For_Keras - keras implenentation (not compartable with retinanet)

[hgaiser]

Hmm interesting suggestion and thank you for the resources! I don't think we will add this anytime soon, but it's interesting to see their results.

[innat-asj]

cc. @gosha20777 @hgaiser
FYI, https://github.com/keras-team/keras-cv

Cutmix, Mixup, MosaicMix, etc all are supported now in core keras. https://keras.io/api/keras_cv/layers/augmentation/