Python: Fix all metrics-related compilation failures

In hindsight, having a `.getMetrics()` method that just returns `this`
is somewhat weird. It's possible that it predates the existence of the
inline cast, however.

python/ql/src/Metrics/LackofCohesionInMethodsCK.ql

@@ -9,6 +9,7 @@
  */
 
 import python
+private import LegacyPointsTo
 
 from ClassMetrics cls
 select cls, cls.getLackOfCohesionCK() as n order by n desc