Tests

Adding back building images with mode=stable #351

Job	Run time
prelim	1s
gpu_image / Build and upload image (a100-40gb-4)	42s
tpu_image / Build and upload image (v4-8)	1m 38s
gpu_integration_tests / run	9m 3s
gpu_unit_tests / run	2m 53s
tpu_unit_tests / run	15m 35s
tpu_integration_tests / run	6m 14s
Clean up	5s
	36m 11s

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