Migration from Anaconda to conda-forge

[yoshipon]

What?

This PR adds a Python setup script for conda-forge. It updates CI, documentation, and tools/Makefile to use setup_miniforge.sh, while keeping the existing recipes to use Anaconda for reproducibility. The setup_miniforge.sh is written by copying setup_anaconda.sh.

Why?

While Anaconda is more reliable as a commercial product, conda-forge is more community-driven and has a permissive license.

See also

https://github.com/conda-forge/miniforge