Python: Fix query tests

Mostly just adding `private import LegacyPointsTo`. Sometimes getting
rid of other imports that are superceded by that module.

python/ql/src/Exceptions/IllegalExceptionHandlerType.ql

@@ -12,6 +12,7 @@
  */
 
 import python
+private import LegacyPointsTo
 
 from ExceptFlowNode ex, Value t, ClassValue c, ControlFlowNode origin, string what
 where

python/ql/src/Exceptions/IllegalRaise.ql

@@ -14,6 +14,7 @@
 import python
 import Raising
 import Exceptions.NotImplemented
+private import LegacyPointsTo
 
 from Raise r, ClassValue t
 where