Trapping, extended to (a) enstrophy, and (b) local trapping

[Jacob-Stevens-Haas]

Here are the changes that Aland and Mai (and to a lesser extent, I) have been working on to expand trapping SINDy to local stability and, in parallel, to trapping enstrophy rather than just energy.

There are a few things to iron out, but I wanted to activate CI tests and merge conflict detection at this point

Remaining:

• [x] verify von karman trapping extended worked on the last commit pre-jake
• [ ] Debug failing fits
  • [ ] Test out different rcond parameters (potentially refactor _update_coef_constraints to be generic equality-constrained least squares
  • [ ] Verify where mod_matrix is used in current iteration of trapping_extended vs previously
  • [ ] Check deeper into the math involved
• [x] Update notebooks to working python scripts
• [x] Update notebook tests to ~install requirements.txt if it exists~ skip experiment 8
• [x] Update doc build to correctly point to all elements of the example
• [x] Replace equations in docstring with rst math/inline-math blocks (::math .. and :math:)

Long term (after this PR, maybe not all)

• move ConstrainedSR3/MIOSR constraints to fit
• Have TrappingSR3 take a PolynomialLibrary as an argument; infer data-dependent params in fit().
• Incorporate notebook metrics to trapping_sr3.py
• Scrub warnings vs intended usage.
• Change names of terms in _objective to be more diagnostically useful
• Add test for inequality + equality constraints

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.

Project coverage is 94.31%. Comparing base (f2cdf2b) to head (94febf9). Report is 16 commits behind head on master.

Files	Patch %	Lines
pysindy/optimizers/constrained_sr3.py	0.00%	1 Missing :warning:
pysindy/optimizers/trapping_sr3.py	95.23%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #536 +/- ## ========================================== + Coverage 94.05% 94.31% +0.26% ========================================== Files 38 37 -1 Lines 4157 4101 -56 ========================================== - Hits 3910 3868 -42 + Misses 247 233 -14 ```

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[Jacob-Stevens-Haas]

I'm going to go ahead and merge this since others are starting to PR changes to master. Fixing the last bit can be done against the master branch, and we don't need to keep extra branches around.