Remove `SET_ENCLOS()` usage

[lionel-]

• Tidy eval: Used to restore data mask top environments after a quosure has been

• r_alloc_empty_environment(): Used in vctrs.

  r_obj* env = Rf_allocSExp(R_TYPE_environment);
  r_env_poke_parent(env, parent);

  Should be able to use the new R_newEnv() API that Luke added 3 years ago.