Add `FalconBackbone` #4645

Job	Run time
Check the code format	2m 2s
Test the code with Keras 3 (tensorflow)	14m 28s
Test the code with Keras 2	17m 48s
Test the code with Keras 3 (jax)	13m 10s
Test the code with Keras 3 (torch)	9m 46s
	57m 14s

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