Add setter for backend

[tmigot]

As mentioned in https://github.com/JuliaSmoothOptimizers/ADNLPModels.jl/pull/55#issuecomment-1109299069

I think we can also close https://github.com/JuliaSmoothOptimizers/ADNLPModels.jl/issues/46 for instance:

using ADNLPModels, NLPModels
nlp = ADNLPModel(sum, ones(3))
grad(nlp, nlp.meta.x0)
set_adbackend!(nlp, gradient_backend = ADNLPModels.ForwardDiffADGradient, x0 = ones(Float32, 3))
grad(nlp, rand(Float32, 3))

[github-actions[bot]]

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[bot]]

Codecov Report

Merging #64 (a627660) into main (e60daaa) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #64      +/-   ##
==========================================
+ Coverage   99.40%   99.42%   +0.01%     
==========================================
  Files           7        7              
  Lines         677      695      +18     
==========================================
+ Hits          673      691      +18     
  Misses          4        4              

Impacted Files	Coverage Δ
src/ADNLPModels.jl	100.00% <100.00%> (ø)

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[dpo]

Sorry, I'm not sure why my comments appear several times...

[github-actions[bot]]

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

[tmigot]

Argh, now the tests fail because of the update of NLPModelsTest and NLPModelsModifiers ...

[github-actions[bot]]

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

[tmigot]

This was waiting for the unit tests to pass, so I will merge.