Compute coloration on the whole Hessian matrix instead of triangle

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (676fa85) 98.25% compared to head (3811bde) 98.25%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #143 +/- ## ======================================= Coverage 98.25% 98.25% ======================================= Files 9 9 Lines 1144 1148 +4 ======================================= + Hits 1124 1128 +4 Misses 20 20 ``` | [Impacted Files](https://app.codecov.io/gh/JuliaSmoothOptimizers/ADNLPModels.jl/pull/143?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers) | Coverage Δ | | |---|---|---| | [src/sparse\_hessian.jl](https://app.codecov.io/gh/JuliaSmoothOptimizers/ADNLPModels.jl/pull/143?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers#diff-c3JjL3NwYXJzZV9oZXNzaWFuLmps) | `92.70% <100.00%> (+0.15%)` | :arrow_up: | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/JuliaSmoothOptimizers/ADNLPModels.jl/pull/143/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers)

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