Should we get rid of tezos_protocol_*_functor?

tezos_protocol_alpha_functor introduces a stack overflow on a tenderbake branch (#1927 (closed)). From ocaml#10734: the file is simply too big for ocamlopt.

This raise the question: should we keep this file (if we don't use it) or separate it between multiple files to avoid potential stack overflows?

(ping @pirbo)