Deprecate and remove BGCDV mode

In #796 we deprecated Dynamic Vegetation mode and required it's use only with the ignore-warnings buildnml option. Since, BGCDV has NOT be scientifically maintained or tested in long simulations and FATES is really taking over this functionality, we'd like to remove it as an option. This means removing it from our testing, and simplify the code and the compsets, and namelist options by removing it as an option. This simplifies our testing, and makes the code easier to understand and support.

Definition of Done:
- [ ] Remove BGCDV from our testing
- [ ] Remove compsets that use it
- [ ] Remove it from the buildnml
- [ ] Remove it from the code