Update config.yml schema to avoid warnings about unused variables

[mnlevy1981]

Is your feature request related to a problem? Please describe.
We running the key metrics example out of a CESM case, the log file has the following warning messages:

These parameters are not used in the task's source code: 'CESM_output_dir', 'base_case_name', 'base_case_output_dir', 'base_end_date', 'base_start_date', 'case_name', 'end_date', 'lc_kwargs', 'obs_data_dir', 'serial', 'start_date', and 'subset_kwargs'
These parameters are not used in the task's source code: 'lc_kwargs', 'serial', and 'subset_kwargs'
These parameters are not used in the task's source code: 'CESM_output_dir', 'base_case_output_dir', 'lc_kwargs', 'obs_data_dir', 'serial', and 'subset_kwargs'
These parameters are not used in the task's source code: 'base_case_name', 'base_case_output_dir', 'base_end_date', 'base_start_date', 'lc_kwargs', 'serial', and 'subset_kwargs'
These parameters are not used in the task's source code: 'subset_kwargs'
These parameters are not used in the task's source code: 'base_start_date', 'lc_kwargs', 'serial', 'start_date', and 'subset_kwargs'

One workaround would be to add one more layer of dictionary to the global parameters in config.yml, and passing a single dictionary of parameters instead of a bunch of individual parameters to each notebook.

Describe the solution you'd like

I think something like

global_params:
+ CUPiD_config:
    case_name: 'b.e30_beta02.BLT1850.ne30_t232.104'
    base_case_name: 'b.e23_alpha17f.BLT1850.ne30_t232.092'
    CESM_output_dir: /glade/campaign/cesm/development/cross-wg/diagnostic_framework/CESM_output_for_testing
    start_date: '0001-01-01'
    end_date: '0101-01-01'
    base_start_date: '0001-01-01'
    base_end_date: '0101-01-01'
    obs_data_dir: '/glade/campaign/cesm/development/cross-wg/diagnostic_framework/CUPiD_obs_data'
    lc_kwargs:
      threads_per_worker: 1

And then notebooks would use CUPiD_config['case_name'] instead of case_name (or create local copies out of the dictionary).

[mnlevy1981]

Note that there are helper scripts that either read or write global_params, so the CUPiD_config key would need to be inserted in them as well