[Migration] Lance, Video modality, Arrow backend fixes, performance improvements.

[sami-bg]

What does this PR do?

• Lance as a storage backend.
• Video as a modality, with SSv2 as a starter dataset.
• Arrow backend memory leak fixed.
• Refactors, and test coverage.
• New core builder classes.
• Performance improvements that make us competitive with HF datasets (both Lance and Arrow backends).
• benchmarks/ directory to run 6 backbones across >50 image datasets - includes some artifacts for the paper that will be removed/simplified in a later PR (i.e. analysis/ subdirectory).
• profiling/ directory to run profiling of arrow, lance backends against HF datasets.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a Github issue? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
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• Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.