Some build-namelist refactoring for FATES/CN fire data

I noticed this in #1264 and addressed some of it there, but didn't finish. There's a bunch of unneeded duplication of fire data variables for FATES and use_cn versions. There's no reason for this duplication. I mostly addressed this for lightning data. Since we want FATES and BGC to use the same datasets it would be best if they aren't duplicated.

The checks for lightning settings should be refactored a bit so that it recognizes when fire data needs to be included and when it doesn't. light_res==none is the flag that lightning data isn't needed. But, it should check the settings of both fire_method and fates_spitfire_mode to see if that's consistent.

Also as part of this I'd like to add more namelist tests for the new FATES modes that currently aren't being tested in the build-namelist unit tester.