Python: Add test for package inside namespace package

Author: tausbn

python/ql/test/experimental/import-resolution-namespace-relative/pkg/helper.py

@@ -1,2 +1,5 @@
 def process(value):
     sink(value) #$ flow=source
+
+def process2(value):
+    sink(value) #$ flow=source

python/ql/test/experimental/import-resolution-namespace-relative/pkg/sub/__init__.py

@@ -0,0 +1,5 @@
+from .. import helper
+
+def use_multi_level_relative():
+    tainted = source()
+    helper.process2(tainted)