Re-factor Configurator Python code.

Nobody has claimed this yet.

The configurator code was one of the first things written by a developer new to Python. It has also not received much attention since it was written.

As such it is in sore need of refactoring, improvement and general tidying up. This will become particularly relevant if and when we decide to integrate it more closely with our new build system.

### Are there any linked Issues or Pull Requests?

_No response_

### Brief description

Early Python code written for the configurator was written before there was a full understanding of the project requirements/coding standards.

This coupled with a significant changes in updating the access pattern to the configuration namelists (#175) means there is significant scope to re-factor the python code in the configurator.

This issue is to refactor/improve the python code in line with a better understanding of lfric projects requirements.

### Further details of the issue.

_No response_

No files, tests, or entry points are named. Start by locating the configurator's Python code, then read issue #175 and the project's requirements and coding standards; done means the configurator is refactored and tidied in line with those standards and remains suitable for closer build-system integration.

Written by the indexing model from the issue text.