Add sparsity_pattern getter for results

[gdalle]

• Bump version to v0.4.4
• Implement a function sparsity_pattern which returns exactly the matrix A that was given to the coloring algorithm. That way, @Vaibhavdixit02 and others won't have to rely on internals to retrieve it.
• Add this new function to test/utils.jl and move some code around there

Note

Until the next breaking version, this effectively imposes that the sparsity pattern should always be stored in the result type (which is true since #126)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (ae7fa30) to head (315d231).
Report is 1 commits behind head on main.

Additional details and impacted files

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##              main      #135   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           11        11           
  Lines          870       871    +1     
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+ Hits           870       871    +1     

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