Compute stats on all the particles

Currently, we are computing the stats only on the hydro particles and the gparts. In this merge request, I am computing on all type of particles (existing and future types). As we are computing the hydro particles independently, we still need to skip them.

src/statistics.c

@@ -255,10 +255,8 @@ void stats_collect_gpart_mapper(void *map_data, int nr_gparts,
     /* Get the particle */
     const struct gpart *gp = &gparts[k];
 
-    /* If the g-particle has a counterpart, ignore it */
-    if (gp->type != swift_type_dark_matter &&
-        gp->type != swift_type_dark_matter_background)
-      continue;
+    /* Ignore the hydro particles as they are already computed */
+    if (gp->type == swift_type_gas) continue;
 
     /* Ignore non-existing particles */
     if (gp->time_bin == time_bin_inhibited ||