Fix #16392: revertCAFs in external interpreter when necessary

We revert CAFs when loading/adding modules in ghci (presumably to refresh execution states and to allow for object code to be unloaded from the runtime). However, with -fexternal-interpreter enabled, we are only doing it in the ghci process instead of the external interpreter process where the cafs are allocated and computed. This makes sure that revertCAFs is done in the appropriate process no matter if that flag is present or not.