replace Diagnostics module with ClimaDiagnostics

[juliasloan25]

Now that ClimaDiagnostics and ClimaAnalysis are more developed packages, we can switch to using those and remove the ClimaCoupler Diagnostics module. This has the benefits of slimming down the coupler codebase, as well as reducing code duplication.

To Do

• [ ] for each variable defined using Diagnostics interface in user_diagnostics.jl, switch to using ClimaAtmos.Diagnostics interface, as in `atmos_extra_diags.jl
  • turbulent_energy_fluxes may require a different solution, as this is calculated in ClimaCoupler only, not atmos
• [ ] use these variables and ClimaAnalysis to make plots analogous to the current "AMIP paperplots" - follow interface used in ci_plots.jl
• [ ] delete: Diagnostics module and tests, user_diagnostics.jl, all other references to Diagnostics module

SDI https://github.com/CliMA/ClimaUtilities.jl/issues/39