[develop]: Add testing chapter to UG

[gspetro-NOAA]

This PR:

• adds a testing chapter to the UPP
• renames docs to doc for NCO compliance
• adds the UFS logo
• adds a linkcheck functionality for the docs
• automates requirements generation with a requirements.in file and pip-tools

Resolves Issue #883

[WenMeng-NOAA]

@gspetro-NOAA Please sync your branch with the latest UPP develop.

[WenMeng-NOAA]

@FernandoAndrade-NOAA You may run the UPP RTs either on Hera and Orion. There should be baseline changes with this PR.

[FernandoAndrade-NOAA]

Just leaving an update here that the Hera RT run is unfortunately still sitting in queue. I will update again once tests have concluded.

[FernandoAndrade-NOAA]

@FernandoAndrade-NOAA You may run the UPP RTs either on Hera and Orion. There should be baseline changes with this PR.

UPP RTs have completed successfully with no changes in results. I believe the fair share values for the epic accounts are currently relatively low, I would expect RTs from my side to take significantly longer until that's resolved.

[WenMeng-NOAA]

This PR is ready for merging.