add WIS2 GDC metrics, update build tooling

[tomkralidis]

This PR:

• adds support for WIS2 GDC metrics (as defined in add GDC metrics to GDC Technical Considerations wis2-guide#211 and https://github.com/wmo-im/wis2-metric-hierarchy/blob/main/metrics/gdc.csv). This is implemented via CLI and Python API such that metrics can be run on any GDC
• updates for Python 3.12 and build tooling

[josusky]

I have fixed a few edge cases, but in general it looks good to me.