add initial commit for routing engine

[ljwolf]

This adds the initial routing engine explained in #464.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 393 lines in your changes missing coverage. Please review.

Project coverage is 67.7%. Comparing base (13ca45e) to head (01f3b51).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
spopt/route/utils.py	0.0%	149 Missing ⚠️
spopt/route/heuristic.py	0.0%	130 Missing ⚠️
spopt/route/engine.py	0.0%	114 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (13ca45e) and HEAD (01f3b51). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (13ca45e)	HEAD (01f3b51)
	8	7

Additional details and impacted files

@@           Coverage Diff            @@
##            main    #465      +/-   ##
========================================
- Coverage   77.8%   67.7%   -10.1%     
========================================
  Files         27      30       +3     
  Lines       2638    3031     +393     
========================================
  Hits        2053    2053              
- Misses       585     978     +393     

Files with missing lines	Coverage Δ
spopt/route/engine.py	0.0% <0.0%> (ø)
spopt/route/heuristic.py	0.0% <0.0%> (ø)
spopt/route/utils.py	0.0% <0.0%> (ø)

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