Change shr_spfn_erfc to erfc intrinsic

at end of all CCPP conversions and when we retire CAM.

This is not isolated to microp_aero where this issue arose (https://github.com/ESCOMP/atmospheric_physics/pull/411), there's hundreds of those in the CAM code.

The issue identifies shr_spfn_erfc occurrences in CAM code, including microp_aero, and notes that there are hundreds across CCPP conversions. Start by inventorying those occurrences and confirming which conversions are in scope with maintainers. Done means all applicable occurrences use the erfc intrinsic while the affected conversions remain valid.

Written by the indexing model from the issue text.