Explicitly define conda environments

Conda environments are currently implicitly defined with just the most high-level dependencies mentioned. This has led to issues in the past:

• https://gitlab.rc.uab.edu/center-for-computational-genomics-and-data-science/sciops/pipelines/quac/-/issues/47
• https://gitlab.rc.uab.edu/center-for-computational-genomics-and-data-science/sciops/pipelines/small_variant_caller_pipeline/-/issues/41

I suspect this will be a bigger issue as time goes by and new version of implicit dependencies become available. So specifying the exact dependency is a good idea to work around this issue.