Registry should allow for registered variables to also be dimensions of other variables

[nusbaume]

What is the feature/what would you like to discuss?

Many registry variables have a dimensions attribute, with most of those dimensions being defined by the CCPP-framework itself. However, it would be beneficial to have the ability to use other registered variables (assuming they are scalar integers with pre-set values) as dimensions when need be, especially for variables that might have specialized or unique dimensions that aren't generally used elsewhere.

Doing this would require generate_registry_data.py to do the following:

1. Check if the dimension names already exist in the registry variable dictionary (if not already one of the official CCPP-framework dimensions)
2. If it does exist in the dictionary, check that the variable is an integer type with no dimensions (i.e. a scalar)
3. Also, check that the variable is either declared a parameter, or has an initial_value attribute.
4. Finally, if all those checks pass, then the script will need to modify the auto-generated code so that the allocation is done with the provided registry variable(s).

Once this work is done, a couple of unit tests could be added to ensure that it works as expected.

Is there anyone in particular you want to be part of this conversation?

@peverwhee @cacraigucar

Will this change (regression test) answers?

No

Will you be implementing this enhancement yourself?

Any Software Engineer can do this

[jimmielin]

Closed by #462