Add documentation and reorganize

[Dekker1]

• Add documentation for all structures in the code base
• Reorganize the order of items in the Rust code for consistency

[codecov]

Codecov Report

Attention: Patch coverage is 77.23330% with 525 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/huub/src/model/flatzinc.rs	59.74%	205 Missing and 45 partials ⚠️
crates/huub/src/solver/engine/int_var.rs	80.39%	68 Missing and 1 partial ⚠️
crates/fzn-huub/src/trace.rs	20.93%	34 Missing ⚠️
crates/huub/src/helpers/linear_transform.rs	44.00%	28 Missing ⚠️
crates/huub/src/solver/engine.rs	83.78%	22 Missing and 2 partials ⚠️
crates/huub/src/propagator.rs	72.50%	21 Missing and 1 partial ⚠️
crates/huub/src/solver/view.rs	74.07%	14 Missing ⚠️
crates/huub/src/solver/value.rs	0.00%	13 Missing ⚠️
crates/huub/src/model/bool.rs	90.16%	11 Missing and 1 partial ⚠️
crates/huub/src/solver/engine/solving_context.rs	83.87%	7 Missing and 3 partials ⚠️
... and 12 more

Files with missing lines	Coverage Δ
crates/fzn-huub/src/lib.rs	46.57% <ø> (ø)
crates/fzn-huub/src/main.rs	39.47% <ø> (ø)
crates/huub/src/brancher.rs	87.09% <ø> (ø)
crates/huub/src/helpers.rs	100.00% <ø> (ø)
crates/huub/src/model/branching.rs	82.60% <ø> (ø)
crates/huub/src/model/constraint.rs	45.18% <ø> (ø)
crates/huub/src/propagator/all_different_int.rs	95.47% <100.00%> (-0.18%)	⬇️
crates/huub/src/propagator/array_int_minimum.rs	96.39% <100.00%> (ø)
crates/huub/src/propagator/int_abs.rs	90.66% <ø> (ø)
crates/huub/src/propagator/int_div.rs	94.55% <ø> (ø)
... and 28 more

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• Flaky Tests Detection - Detect and resolve failed and flaky tests

[codspeed-hq]

CodSpeed Performance Report

Merging #139 will not alter performance

_{Comparing Dekker1:fix/docs (c027df7) with develop (4aa742b)}

Summary

✅ 13 untouched benchmarks