Coil forces

[smhurwitz]

This is to pull all the force optimization work into master.

[landreman]

In selffield.py, the functions G, K, local_field, local_field_rect, field_from_other_coils, and field_from_other_coils_pure are not used in any test or example. Codecov is flagging these functions for having no test coverage. The function local_field_rect would need some work anyway to use a general frame instead of the Frenet frame, and both local_field_rect, field_from_other_coils should be vectorized to avoid the explicit for loop. So, I propose we remove these functions for now from the PR, since getting these functions polished and tested would delay the merge of the functions for Lorentz force, and they can be merged in a separate PR later. If anyone objects, let me know.

[codecov]

Codecov Report

Attention: Patch coverage is 99.32432% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.68%. Comparing base (988e15c) to head (27f3959).
Report is 85 commits behind head on master.

Files with missing lines	Patch %	Lines
src/simsopt/geo/curve.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #450      +/-   ##
==========================================
+ Coverage   92.61%   92.68%   +0.06%     
==========================================
  Files          75       77       +2     
  Lines       13837    13982     +145     
==========================================
+ Hits        12815    12959     +144     
- Misses       1022     1023       +1     

Flag	Coverage Δ
unittests	92.68% <99.32%> (+0.06%)	⬆️

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[landreman]

Hearing no objections, I'll merge.