Add lin_nnzj and nln_nnzj and docstrings for functions

[arnavk23]

This PR adds the lin_nnzj and nln_nnzj fields to the output of the show method for AbstractNLPModelMeta and documents the purpose and usage of the scaling-related functions exported in the NLPModels API: varscale, lagscale, and conscale.

Closes #485
Closes #413

[arnavk23]

@amontoison please review the changes made here

[amontoison]

@arnavk23 I will review the PR asap.

[amontoison]

CI failures are related.

[tmigot]

@arnavk23 I checked the issue #413 and to close we would need to add lin_nnzj and nln_nnzj in the README.md as well.

[arnavk23]

@tmigot can you review the changes made

[tmigot]

You have to change
https://github.com/JuliaSmoothOptimizers/NLPModels.jl/blob/main/test/nlp/show.jl
and maybe this
https://github.com/JuliaSmoothOptimizers/NLPModels.jl/blob/main/test/nls/show.jl
so that the tests pass.
Can you also edit the README.md in this PR?

Thank you!

[arnavk23]

@tmigot I have passed both for SimpleNLPModel but for Generic even when the showed and the expected are the same, it is throwing an error for both test/nlp/show.jl and test/nls/show.jl

[arnavk23]

@tmigot this is what is coming as I was saying above -

Expression: strip.(split(chomp(showed), "\n")) == strip.(split(chomp(expected), "\n"))
Evaluated: SubString{String}["Problem name: Generic", "All variables: ████████████████████ 1 All constraints: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "free: ████████████████████ 1 free: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "lower: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 lower: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "upper: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 upper: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "low/upp: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 low/upp: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "fixed: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 fixed: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "infeas: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 infeas: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "nnzh: ( 0.00% sparsity) 1 linear: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "nonlinear: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "nnzj: (------% sparsity)", "lin_nnzj: (------% sparsity)", "nln_nnzj: (------% sparsity)", ""] == SubString{String}["Problem name: Generic", "All variables: ████████████████████ 1 All constraints: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "free: ████████████████████ 1 free: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "lower: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 lower: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "upper: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 upper: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "low/upp: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 low/upp: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "fixed: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 fixed: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "infeas: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0 infeas: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "nnzh: ( 0.00% sparsity) 1 linear: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "nonlinear: ⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅ 0", "nnzj: (------% sparsity)", "lin_nnzj: (------% sparsity)", "nln_nnzj: (------% sparsity)"]

Stacktrace:
[1] macro expansion
@ ~/hostedtoolcache/julia/1.11.5/aarch64/share/julia/stdlib/v1.11/Test/src/Test.jl:679 [inlined]
[2] macro expansion
@ ~/work/NLPModels.jl/NLPModels.jl/test/nlp/show.jl:49 [inlined]
[3] macro expansion
@ ~/hostedtoolcache/julia/1.11.5/aarch64/share/julia/stdlib/v1.11/Test/src/Test.jl:1704 [inlined]
[4] top-level scope
@ ~/work/NLPModels.jl/NLPModels.jl/test/nlp/show.jl:2
Test Summary: | Pass Fail Total Time
Increase coverage of nlp/show.jl | 1 1 2 2.0s
ERROR: LoadError: Some tests did not pass: 1 passed, 1 failed, 0 errored, 0 broken.
in expression starting at /Users/runner/work/NLPModels.jl/NLPModels.jl/test/nlp/show.jl:1
in expression starting at /Users/runner/work/NLPModels.jl/NLPModels.jl/test/runtests.jl:9
Package NLPModels errored during testing
Error: Process completed with exit code 1.

[arnavk23]

@amontoison @tmigot I have checked it on my system now properly, it works. It should be passing all the tests now.

[arnavk23]

@amontoison @tmigot It passes all tests except the breakage/upload one

[tmigot]

Thanks @arnavk23 !