What does this PR do?

This PR removes attack-specific optimizers and moves them to be generic PL optimizers.

Depends upon #146.

Type of change

Please check all relevant options.

[ ] Improvement (non-breaking)
[ ] Bug fix (non-breaking)
[ ] New feature (non-breaking)
[x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update

Please describe the tests that you ran to verify your changes. Consider listing any relevant details of your test configuration.

[x] pytest
[x] python -m mart experiment=CIFAR10_CNN_Adv trainer=gpu achieves 71% accuracy.

[x] The title is self-explanatory and the description concisely explains the PR
[x] My PR does only one thing, instead of bundling different changes together
[x] I list all the breaking changes introduced by this pull request
[x] I have commented my code
[x] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[x] I have run pre-commit hooks with pre-commit run -a command without errors

Make sure you had fun coding 🙃