aggregate.py: add format=latest_grouped #4718

Job	Run time
Build XLA / build	1h 0m 28s
Build & publish docs	0s
GPU tests / test (benchmark_tests)	13m 29s
GPU tests / test (cpp_tests1)	20m 0s
GPU tests / test (cpp_tests2)	28m 35s
GPU tests / test (python_tests, xla_op1)	1h 5m 36s
CPU tests / test (benchmark_tests)	11m 19s
GPU tests / test (python_tests, xla_op2)	51m 0s
CPU tests / test (cpp_tests1)	15m 50s
GPU tests / test (python_tests, xla_op3)	53m 47s
CPU tests / test (cpp_tests2)	18m 6s
GPU tests / test (python_tests, torch_mp_op)	1h 37m 31s
CPU tests / test (python_tests, xla_op1)	18m 52s
CPU tests / test (python_tests, xla_op2)	11m 13s
CPU tests / test (python_tests, xla_op3)	12m 27s
CPU tests / test (python_tests, torch_mp_op)	30m 43s
	8h 28m 56s

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