Add basic MPI logging capabilities

[nefrathenrici]

This PR implements two loggers using LoggingExtras.jl. These loggers do not change the ClimaComms API.

• MPILogger(ctx, iostream = stdout): This adds a ClimaComms PID prefix in front of each log message, for example [P1] Info: smoke test
• MPIFileLogger(ctx, log_dir): Log MPI ranks to different files within the log_dir.

A few questions

• Should we have a default logger constructor depending on the context? Should the MPILogger only be used if MPI is initialized?
• What should the minimal compat be for Logging? It could be set higher

[charleskawczynski]

I do like the idea of some of these helpers, but I think the optional contexts introduces some risk.

Also, the macros look risky to me, partly for the same reason (what is the default? will it match what the user has if it's different?). The macros are a bit difficult to extend, I'm not sure they're buying us anything useful other than hiding conditionals

[nefrathenrici]

Thanks for the feedback, I removed the root macros/loggers and made the comms context the first argument for both remaining loggers:

• MPIFileLogger(ctx, log_dir)
• MPILogger(ctx, iostream = stdout)