More optimization for the decompression of the acyclic coloring

[amontoison]

Related to #68

• Efficient implementation of TreeSetColoringResult

[codecov]

Codecov Report

Attention: Patch coverage is 97.67442% with 1 line in your changes missing coverage. Please review.

Project coverage is 98.21%. Comparing base (b6c38d9) to head (fd8d6fb).

Files	Patch %	Lines
src/decompression.jl	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #73      +/-   ##
==========================================
- Coverage   98.37%   98.21%   -0.16%     
==========================================
  Files          10        9       -1     
  Lines         614      561      -53     
==========================================
- Hits          604      551      -53     
  Misses         10       10              

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[amontoison]

@gdalle
The PR is ready.
We have the optimal structure for decompression and, in my opinion, the best method to compute it.
The only potential improvement could be to apply tricks to minimize dynamic allocations and reuse existing storage.
We can further optimize the code if, one day, someone encounters an issue with a very large graph.