WIP: add unconstrained tests for all optimizers

[ewu63]

Purpose

So a bunch of these tests do not pass...

Expected time until merged

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[marcomangano]

The windows action failure is due to a (temporary?) failure to download the miniconda executables from the official repo.

Ensuring installer...
  Can we use bundled Miniconda?
  Can we download a custom installer by URL?
  Can we download Miniforge?
  ... will download Miniforge.
  Will fetch Mambaforge latest from https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-Windows-x86_64.exe
  Ensuring Installer...
  Checking for cached Mambaforge@latest...
  Did not find Mambaforge-Windows-x86_64.exe latest in cache