micro_vap_liq_exchange output is non-BFB on restarts

micro_liq_ice_exchange, micro_vap_ice_exchange, and micro_vap_liq_exchange are diagnostic outputs from p3. They are not used for anything within the code. They exhibit roundoff-level differences in ERS tests. We should fix this, but don't really use them so it hasn't been a priority. Instead, we keep deleting them from the default output, but every few months a do-gooder adds them back and is surprised when we start failing.

Start by locating the p3 diagnostic outputs micro_liq_ice_exchange, micro_vap_ice_exchange, and micro_vap_liq_exchange, then inspect the ERS restart tests that show roundoff-level differences. Determine how these outputs are produced and what change would make them BFB on restarts; done means the diagnostic outputs no longer cause ERS failures or require repeated removal from default output.

Written by the indexing model from the issue text.