Add support for passing bounds through to NonlinearSolve

[JamesWrigley]

Fixes #84. One oddity is the support for ModifiedKingCurveAlgorithm that can use KingCurveAlgorithm internally, which does not support bounds because it's a linear fit. I opted to strip the bounds before passing the problem to KingCurveAlgorithm, but one could argue that it's better to not support bounds at all if not all parts of the algorithm supports it.

Also refactored the tests a bit to make it easier to filter them. To reviewers, I've tried to keep the commits atomic so I'd recommend reviewing them one-by-one.

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API