initialize comms contexts

[juliasloan25]

Is your feature request related to a problem? Please describe. We use ClimaComms communications contexts for all of our experiments. These contexts are meant to be initialized before they're first used, but it's only really required when running with MPI. Even though we aren't running with MPI currently, it's more complete to initialize our contexts.

Describe the solution you'd like

• [ ] go through all experiments and call ClimaComms.init(context) for each context