Many entries in drv's config_component should be moved to a shared location

Motivated by #3508 and the need to open a similar PR for a subset of that in the cmeps repository (https://github.com/ESCOMP/CMEPS/pull/62): I noticed that there are a lot of xml variables defined in the driver's config_component.xml file that are really not specific to a particular driver, and end up needing to be duplicated for all drivers. For example, various directories (`CIME_OUTPUT_ROOT`, `EXEROOT`, etc.). The decision to put these in the driver's config_component.xml was okay when we only had one driver. But now that we have three drivers, one of which is in a completely different repository, this leads to error-prone duplication and friction when making any changes to this file. This problem is made worse by the fact that `case.get_value` calls appear to silently return some default value rather than failing if a variable isn't defined: this could lead to subtle buggy behavior if someone adds a variable in the mct driver but forgets to add this new variable to cmeps.

This is not just a theoretical issue: I found that the NONLOCAL variable hadn't been added to CMEPS's config_component (and I wouldn't be surprised if there are others).

I suggest that we pull all non-driver-specific variables out of the driver's config_component file into some other file that is shared between all drivers.