Split GetShortestPath methods to smaller files

[viceroypenguin]

This PR migrates the various Dijkstra and A* methods to different files for easier maintainability in the future.

[codecov]

Codecov Report

Patch coverage: 98.14% and no project coverage change.

Comparison is base (1f68ffa) 93.02% compared to head (916d69c) 93.02%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #511   +/-   ##
=======================================
  Coverage   93.02%   93.02%           
=======================================
  Files         249      253    +4     
  Lines        8184     8184           
  Branches     1635     1635           
=======================================
  Hits         7613     7613           
  Misses        358      358           
  Partials      213      213           

Files Changed	Coverage Δ
Source/SuperLinq/GetShortestPathCost.Dijkstra.cs	97.14% <97.14%> (ø)
Source/SuperLinq/GetShortestPathCost.A-Star.cs	97.91% <97.91%> (ø)
Source/SuperLinq/GetShortestPath.Dijkstra.cs	98.03% <98.03%> (ø)
Source/SuperLinq/GetShortestPath.A-Star.cs	98.21% <98.21%> (ø)
Source/SuperLinq/GetShortestPaths.cs	100.00% <100.00%> (ø)

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