`fre.cmor`: update `fre cmor varlist` for new modeler name -> mip table name mapping

[ilaflott]

this is about right.

i want to adjust fre cmor varlist too for the new approach, but this PR is already bloated, so i'm cutting myself off.

Originally posted by @ilaflott in #846 (comment)

basically, if the found variable is in a mip table, set the value equal to the key. otherwise, leave the value as an empty string, if something like --include-modeler-vars is specified on the CLI.