Add support for all image classifier backbones to the image embedder

[ethanwharris]

What does this PR do?

Part of #1031

Breaking changes

• Removes the dino strategy (used to work only on GPU)
• Removes the MOCO strategy (wasn't working anyway)

Before submitting

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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]
• Did you verify new and existing tests pass locally with your changes?
• If you made a notable change (that affects users), did you update the CHANGELOG?

PR review

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Anyone in the community is free to review the PR once the tests have passed.
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[codecov]

Codecov Report

Merging #1264 (a0b518a) into master (df67f87) will decrease coverage by 1.53%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1264      +/-   ##
==========================================
- Coverage   91.19%   89.65%   -1.54%     
==========================================
  Files         286      284       -2     
  Lines       12791    12745      -46     
==========================================
- Hits        11665    11427     -238     
- Misses       1126     1318     +192     

Flag	Coverage Δ
unittests	89.65% <100.00%> (-1.54%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...lash/image/embedding/vissl/transforms/multicrop.py	98.11% <ø> (ø)
...lash/image/embedding/vissl/transforms/utilities.py	100.00% <ø> (+17.07%)	⬆️
flash/image/embedding/heads/vissl_heads.py	100.00% <100.00%> (ø)
flash/image/embedding/losses/vissl_losses.py	100.00% <100.00%> (ø)
flash/image/embedding/model.py	98.38% <100.00%> (+0.34%)	⬆️
...ash/image/embedding/strategies/vissl_strategies.py	100.00% <100.00%> (ø)
...ash/image/embedding/transforms/vissl_transforms.py	100.00% <100.00%> (ø)
flash/image/embedding/vissl/adapter.py	93.75% <100.00%> (+1.35%)	⬆️
flash/image/embedding/vissl/transforms/__init__.py	100.00% <100.00%> (ø)
flash/text/classification/input.py	53.33% <0.00%> (-46.67%)	⬇️
... and 19 more

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