insert torchvision dependency and write tests for cifar10

[BaruchG]

What does this PR do?

Wrote unit test for the CIFAR10 dataset and made the dataset import from torchvision to reduce code redundancy as outlined in #839.

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• Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
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• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests? [not needed for typos/docs]
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PR review

• Is this pull request ready for review? (if not, please submit in draft mode)
  Draft proposal since TrialCifar10 explicitly states that it should not rely on torchvision and this PR makes CIFAR10 a torchvision dependency.

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[oke-aditya]

Eh it didn't merge cleanly.

[otaj]

Fixed

[otaj]

Hi @BaruchG, can I ask why was this closed?

[BaruchG]

Sorry @otaj, I was having some issues with my github version and this somehow got deleted. The branch is now up again at https://github.com/BaruchG/lightning-bolts/tree/cifar until we decide on what to do with hard torchvision dependencies.