Speed up SBR tests, and add NUTS kwargs

[Jacob-Stevens-Haas]

This PR implements some changes to testing:

1. Tests involving SBR use a much smaller num_warmup, num_samples than the default arguments.
2. nuts_kwargs added to allow fine control of the sampler (to allow faster termination in tests)
3. column normalization is extracted from BaseOptimizer.fit so that it can be tested independently. The test no longer is parametrized across all subclasses, but rather just tests the helper function.
4. Do a few more notebook tests in CI

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.28%. Comparing base (4d27145) to head (ddf8d6d).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #573      +/-   ##
==========================================
- Coverage   95.31%   95.28%   -0.04%     
==========================================
  Files          37       38       +1     
  Lines        4059     4069      +10     
==========================================
+ Hits         3869     3877       +8     
- Misses        190      192       +2     

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