[nRF Cloud] renaming of API Resources 🛑 GPS 🆗 GNSS

[coderbyheart]

The following API resources will be renamed to use correct term GNSS in favor of the specific constellation name GPS.

This affects the REST API:

• GET location/agps → POST location/agnss

And the MQTT API, however this is handled in nRF Connect SDK, so no change needed for nRF Asset Tracker.

• AGPS → AGNSS

Note: Predicted GPS is not renamed, because only GPS is support for predictions right now on the device side

Tasks

• Rename A-GPS to A-GNSS #840
• [nRF Cloud] rename API endpoints asset-tracker-cloud-aws-js#1422
• [nRF Cloud] rename API endpoints asset-tracker-cloud-azure-js#590
• Rename API endpoints nrfcloud-location-services-tests-js#134