daemon: use __attribute__((constructor)) for protolayer_globals

The protolayer_globals array can basically be treated as a constant by most of the program and its initialization only uses compile-time-known values. We basically only initialize parts of the array in different files throughout the codebase to maintain separation of concerns, so that each piece of Knot Resolver initializes the part that pertains to it. Therefore, I believe that it is more ergonomic to just use __attribute__((constructor)) for these functions, so as not to pollute daemon/main.c with these calls.