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/FLinesOfCode.ql

@@ -11,7 +11,8 @@
  */
 
 import python
+private import LegacyPointsTo
 
-from Module m, int n
-where n = m.getMetrics().getNumberOfLinesOfCode()
+from ModuleMetrics m, int n
+where n = m.getNumberOfLinesOfCode()
 select m, n order by n desc