Add Symbolics as optional dep

[tmigot]

This also enables the possibility to provide the Jacobian/Hessian sparsity pattern manually.

[github-actions]

Package name	latest	stable
CaNNOLeS.jl
DCISolver.jl
DerivativeFreeSolvers.jl
JSOSolvers.jl
NLPModelsIpopt.jl
OptimizationProblems.jl
Percival.jl
QuadraticModels.jl
SolverBenchmark.jl
SolverTools.jl

[codecov]

Codecov Report

Patch coverage: 92.04% and project coverage change: +0.04 🎉

Comparison is base (1b615ea) 93.40% compared to head (a82b674) 93.44%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #177      +/-   ##
==========================================
+ Coverage   93.40%   93.44%   +0.04%     
==========================================
  Files          13       14       +1     
  Lines        1622     1633      +11     
==========================================
+ Hits         1515     1526      +11     
  Misses        107      107              

Impacted Files	Coverage Δ
src/predefined_backend.jl	100.00% <ø> (ø)
src/sparse_sym.jl	91.25% <91.25%> (ø)
src/ADNLPModels.jl	98.43% <100.00%> (+0.13%)	⬆️
src/sparse_diff_tools.jl	87.03% <100.00%> (ø)
src/sparse_hessian.jl	100.00% <100.00%> (+5.64%)	⬆️
src/sparse_jacobian.jl	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.