Keras community call outlines pluggable backends and KerasHub updates

Keras is moving to a pluggable backend design, with MLX and PaddlePaddle backends upcoming as add-on libraries. The team is reducing the operations needed to ship new backends and streamlining unit testing so a single harness can test all ops, such as casting consistency. KerasHub also gains many new models and is shifting its preprocessing from tf-text to PyGrain.