compiler: Use cached_property where useful

Author: FabioLuporini

devito/ir/clusters/cluster.py

@@ -690,15 +690,15 @@ def dspace(self):
         """Return the DataSpace of this ClusterGroup."""
         return DataSpace.union(*[i.dspace.reset() for i in self])
 
-    @property
+    @cached_property
     def is_dense(self):
         return all(i.is_dense for i in self)
 
-    @property
+    @cached_property
     def is_wild(self):
         return all(i.is_wild for i in self)
 
-    @property
+    @cached_property
     def is_halo_touch(self):
         return all(i.is_halo_touch for i in self)