argmin_testfunctions: Edition 2021, approx crate in tests, fixed size input arrays, const generic Rosenbrock derivative and Hessian

[stefan-k]

• It's 2024!
• Set edition 2021 for testfunctions crate
• Use fixed size input arrays for test functions which work only on a fixed number of parameters. Therefore these test functions do not panic anymore.
• Added const generic variants of the Rosenbrock derivative and Hessian. Compared to the non-const variants, those do not allocate.

[codecov-commenter]

Codecov Report

Attention: 46 lines in your changes are missing coverage. Please review.

Comparison is base (a62f6aa) 90.51% compared to head (e588301) 90.39%.

Files	Patch %	Lines
tools/testfunctions/src/rosenbrock.rs	28.81%	42 Missing ⚠️
tools/testfunctions/src/sphere.rs	77.77%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #414      +/-   ##
==========================================
- Coverage   90.51%   90.39%   -0.12%     
==========================================
  Files         162      162              
  Lines       20373    20573     +200     
==========================================
+ Hits        18440    18597     +157     
- Misses       1933     1976      +43     

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