DRAFT: adding Spectral cones

[Transurgeon]

Description

Please include a short summary of the change.
TODO:

• add tests for the exotic2common.
• make sure the logdet cone constraint is added to the SCS interface
• deal with when to call the exotic2common reduction vs. when to just pass the logdet cone
  Issue link (if applicable):

Type of change

• New feature (backwards compatible)
• New feature (breaking API changes)
• Bug fix
• Other (Documentation, CI, ...)

Contribution checklist

• Add our license to new files.
• Check that your code adheres to our coding style.
• Write unittests.
• Run the unittests and check that they’re passing.
• Run the benchmarks to make sure your change doesn’t introduce a regression.