Replaces Optimization dependency with OptimizationBase

[nicholaskl97]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Optimization v5 was recently released, prompting this change. The new compat entry for OptimizationBase includes v3, which should work, but has not been tested, since NeuralPDE currently requires Optimization v4, limiting OptimizationBase to v2.

Also uses [sources] in Project.toml to use local NeuralLyapunovProblemLibrary in testing instead of doing it in runtests.jl via Pkg.