core: remove ManagerRunningAs enum

Previously, we had two enums ManagerRunningAs and UnitFileScope, that were
mostly identical and converted from one to the other all the time. The latter
had one more value UNIT_FILE_GLOBAL however.

Let's simplify things, and remove ManagerRunningAs and replace it by
UnitFileScope everywhere, thus making the translation unnecessary. Introduce
two new macros MANAGER_IS_SYSTEM() and MANAGER_IS_USER() to simplify checking
if we are running in one or the user context.

src/systemctl/systemctl.c

@@ -4810,7 +4810,7 @@ static int cat(int argc, char *argv[], void *userdata) {
                 return -EINVAL;
         }
 
-        r = lookup_paths_init_from_scope(&lp, arg_scope, arg_root);
+        r = lookup_paths_init(&lp, arg_scope, arg_root);
         if (r < 0)
                 return log_error_errno(r, "Failed to determine unit paths: %m");
 
@@ -5241,7 +5241,7 @@ static int enable_sysv_units(const char *verb, char **args) {
         /* Processes all SysV units, and reshuffles the array so that
          * afterwards only the native units remain */
 
-        r = lookup_paths_init(&paths, MANAGER_SYSTEM, false, arg_root);
+        r = lookup_paths_init(&paths, arg_scope, arg_root);
         if (r < 0)
                 return r;
 
@@ -6074,7 +6074,7 @@ static int find_paths_to_edit(sd_bus *bus, char **names, char ***paths) {
         assert(names);
         assert(paths);
 
-        r = lookup_paths_init_from_scope(&lp, arg_scope, arg_root);
+        r = lookup_paths_init(&lp, arg_scope, arg_root);
         if (r < 0)
                 return r;