Tests

Add `pad_to_aspect_ratio` flag to ImageConverter #6848

Job	Run time
Test the code (tensorflow, keras-stable)	26m 50s
Check the code format	1m 53s
Test the code (jax, keras-stable)	33m 21s
Test the code (torch, keras-stable)	16m 10s
Test the code (jax, keras-3.5)	33m 9s
Test the code (jax, keras-nightly)	34m 3s
	2h 25m 26s

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