Add precompilation workload

[gdalle]

This speeds up time-to-first-plot tremendously.

Benchmark (to run in a fresh Julia session):

using LinearAlgebra, Random, SparseArrays
using SparseMatrixColorings

# simple task
@time begin
    A = sprand(MersenneTwister(0), Bool, 10, 10, 0.2)
    problem = ColoringProblem(; structure=:nonsymmetric, partition=:column)
    algo = GreedyColoringAlgorithm(; decompression=:direct)
    result = coloring(A, problem, algo)
    B = compress(A, result)
    decompress(B, result)
end;

# complicated task
@time begin
    A = sprand(MersenneTwister(0), Bool, 10, 10, 0.2)
    problem = ColoringProblem(; structure=:nonsymmetric, partition=:bidirectional)
    algo = GreedyColoringAlgorithm(; decompression=:substitution, postprocessing=true)
    result = coloring(A, problem, algo)
    Br, Bc = compress(A, result)
    decompress(Br, Bc, result)
end;

With precompilation:

• Simple task: 0.000096 seconds (108 allocations: 26.328 KiB)
• Complicated task: 0.003747 seconds (1.81 k allocations: 112.008 KiB, 98.13% compilation time)

Without precompilation:

• Simple task: 0.394682 seconds (2.78 M allocations: 141.290 MiB, 1.76% gc time, 99.95% compilation time)
• Complicated task: 0.896819 seconds (3.00 M allocations: 154.698 MiB, 1.33% gc time, 99.98% compilation time)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (172fd12) to head (1675a69).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #252   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        16    +1     
  Lines         1833      1844   +11     
=========================================
+ Hits          1833      1844   +11     

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