Support SubSplitInfo in MultiSplitInfo. #10576

Job	Run time
Check whether we should run tests or not	9s
Github API tests	3m 28s
HuggingFace Python 3.10 tests	3m 18s
Notebook tests	6m 49s
Core TFDS tests / Generate shards	1s
Core TFDS tests / [Python 3.10][1/4]	6m 12s
Core TFDS tests / [Python 3.11][1/4]	5m 48s
Core TFDS tests / [Python 3.12][1/4]	6m 16s
Core TFDS tests / [Python 3.10][2/4]	5m 33s
Core TFDS tests / [Python 3.11][2/4]	5m 34s
Core TFDS tests / [Python 3.12][2/4]	5m 34s
Core TFDS tests / [Python 3.10][3/4]	5m 43s
Core TFDS tests / [Python 3.11][3/4]	5m 48s
Core TFDS tests / [Python 3.12][3/4]	6m 7s
Core TFDS tests / [Python 3.10][4/4]	5m 59s
Core TFDS tests / [Python 3.11][4/4]	6m 16s
Core TFDS tests / [Python 3.12][4/4]	6m 36s
	1h 25m 11s

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