Speed up LargestFirst order

[gdalle]

• Speed up degree computation in adjacency graphs with a diagonal
• Compute the degree of each vertex once and store it before sorting
• Avoid fill!(visited, false) in other places when only some coefficients have been set to true

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (5572dab) to head (e332ee8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #241   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines         1781      1793   +12     
=========================================
+ Hits          1781      1793   +12     

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[gdalle]

Merging since this is a very easy one