Update NUTS3 data to higher resolution and 2016

[cpschau]

The NUTS3 shapes have been updated from a 1:60M resolution (red) to a more detailed 1:3M resolution (blue). Additionally, the base year for these shapes, as well as for other datasets resolved at the NUTS3 level, has been updated from 2013 to 2016. The data is now directly retrieved from Eurostat and GISCO, making the previously used resources, which are part of the data bundle hosted on Zenodo, redundant and removable.

Additionally, data for the UK is retrieved from the Office for National Statistics, as the country is no longer included in regional Eurostat data due to Brexit. Since GDP statistics are not available at the NUTS3 level, Gross Value Added is used instead.

Checklist

• [ ] I tested my contribution locally and it seems to work fine.
• [x] Code and workflow changes are sufficiently documented.
• [x] Changed dependencies are added to envs/environment.yaml.
• [x] Changes in configuration options are added in all of config.default.yaml.
• [x] Changes in configuration options are also documented in doc/configtables/*.csv.
• [ ] A release note doc/release_notes.rst is added.

[fneum]

superseded by https://github.com/PyPSA/pypsa-eur/pull/1286