Add countries_names.json data mapping

[daquinoaldo]

Add a mapping between countries' full names and their coordinates.
Needed for GCP integration: countries are exported with their full names, not their initials.

[CLAassistant]

All committers have signed the CLA.

[amotl]

Dear Aldo,

according to grafana-toolbox#108, the future of maps in Grafana will be the new Geomap panel, so your improvement should be directed to this implementation for Grafana >=8.1.

However, we will also be happy to receive a corresponding patch at our friendly fork https://github.com/panodata/panodata-map-panel. We will probably keep maintaining this for a while until Geomap will be stable and mature. In this manner, others who will also continue to use the vanilla Worldmap panel for a while, can benefit from your improvement.

With kind regards,
Andreas.

[daquinoaldo]

Thank you, Andreas.
I'll open the same PR on the fork, and I'll explore the new panel as soon as the new version is released.

[amotl]

Dear Aldo,

thanks a stack for submitting grafana-toolbox#117 the other day. I will try to have a look at this patch soonish.

With kind regards,
Andreas.