Area is not set for NUOPC single point cases

### Brief summary of bug

@swensosc and Meg Fowler report this. Area is set to missing value 1.e36 when running with SCAM and nuopc (so PTS_MODE with nuopc).

### General bug information

**CTSM version you are using:** latest master

**Does this bug cause significantly incorrect results in the model's science?** No -- unless area is needed (such as hillslope model)

**Configurations affected:** PTS_MODE
### Details of bug

area is read in for PTS_MODE in MCT from the surface dataset, but the new process for setting latitudes and longitudes in NUOPC seems to neglect area.

@mvertens I wanted to point this out to you. I don't think this should be hard to fix. We should be able to read it from the surface dataset in every case. But, if you have other thoughts on this feel free to add them.