MR Spin Integration

[brianz98]

This PR implements spin integraion wrt a multideterminantal reference.

Todos

• Inter-general elementary contractions
• PyBind API additions
• Miscellaneous utilities for MR spin integration
• Enable GHA testing
• Ready to go

[codecov]

Codecov Report

Attention: Patch coverage is 91.47287% with 11 lines in your changes missing coverage. Please review.

Project coverage is 84.94%. Comparing base (a6f7b59) to head (67ca107).

Files	Patch %	Lines
wicked/algebra/equation.cc	33.33%	4 Missing ⚠️
wicked/algebra/index.cc	0.00%	2 Missing ⚠️
...d/diagrams/wick_theorem_elementary_contractions.cc	97.56%	2 Missing ⚠️
...cked/diagrams/wick_theorem_process_contractions.cc	87.50%	2 Missing ⚠️
wicked/algebra/symbolic_term.cc	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #20      +/-   ##
==========================================
+ Coverage   83.92%   84.94%   +1.01%     
==========================================
  Files          48       48              
  Lines        1873     1979     +106     
==========================================
+ Hits         1572     1681     +109     
+ Misses        301      298       -3     

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