Make modules that depend on ClimaComms into an extension?

I have developed some reasonably generic methods attaching compact, verbose, and parseable `Base.show` representations of structs (usually, parameter structs), see [CloudMicrophysics.jl/src/show.jl](https://github.com/CliMA/CloudMicrophysics.jl/blob/main/src/show.jl). I think this package potentially could be a good home for that code.

However, this package currently depends on ClimaComms. Consequently, if a downstream package wants to adopt these custom show methods, it would also need to (indirectly) depend on ClimaComms, which seems unnecessary.

As such, I wonder if the modules/functions that use `ClimaComms` could be put into a package extension?

Start by reading CloudMicrophysics.jl/src/show.jl and locating the ClimaComms-dependent modules in ClimaUtilities.jl. Determine which functionality can be moved behind a package extension while keeping the generic show methods usable without ClimaComms; done means downstream users can adopt those methods without an indirect ClimaComms dependency.

Written by the indexing model from the issue text.