Use Conda lock files

[ewels]

Conda environment.yml files are convenient and easy to use, but do not confer a high degree of reproducibility. Because lower level dependencies are not pinned, the exact build produced can change over time.

To address this without losing the ease of use of environment.yml files, several community projects have emerged to create "lock files", comparable to the Javascript npm community which has package.json and package-lock.json. The most popular for conda is conda-lock.

We should automatically generate conda lock files and store them in git for modules, alongside the conda environment.yml files. We should have CI to regenerate these whenever there is an edit to environment.yml.