Take advantage of validation described in configuration metadata

The only validation of loaded configuration currently undertaken is to check against a list of required namelists. This list is static, so can't take into account namelists conditional on other settings, and is manually maintained, which means it isn't.

There is a wealth of validation rules in the configuration metadata which we might take advantage and automatically generate validation source.

It is not enough to rely on Rose to do the validation as we have no guarantee that the namelists we are loading were generated by Rose.

Start by locating the code that loads configuration and currently checks the manually maintained required-namelist list, then inspect the configuration metadata containing validation rules. Define completion as automatically generated validation that handles conditional namelists and does not depend on Rose-generated input.

Written by the indexing model from the issue text.