improve dependency installation on cloud

[aryarm]

the google life sciences api creates a new snakemake container to run each of our jobs
so our dependencies must be installed anew by snakemake every time it runs a job, since each job is run in a new, empty container
this process may add substantially to the runtime of some of our instances and the cost of using them

we have two options:

1. separate our dependencies into different env files to install only the necessary dependencies for each job
2. create a custom snakemake container with our dependencies already installed in it and force snakemake to use our container instead of its own