Revision of dataset normalizations

[matsumotosan]

What does this PR do?

Fixes part of #839

• pl_bolts.transforms.dataset_normalizations
• pl_bolts.tests.transforms.test_normalizations

Summary

• Typing hints for each dataset normalization function
• Tests for checking if normalizations return tensors of correct shape

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[otaj]

Hi, @matsumotosan, it looks good, thank you!