Remove mamba commands and switch to Miniforge

[xylar]

Yet again, I ran into problems with the mamba command today. It seems it is time to abandon it and return to the conda command instead (along with the libmamba solver).

Checklist

• User's Guide has been updated
• Developer's Guide has been updated
• Documentation has been built locally and changes look as expected
• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

[xylar]

Testing

I installed Miniforge3 using ./conda/configure_compass_env.py and created a development environment.

I also created a development environment using an existing Mambaforge installation and that worked fine.