Python: move shared dataflow to experimental

python/ql/test/experimental/dataflow/local.expected

@@ -0,0 +1,4 @@
+ERROR: Could not resolve module DataFlow (local.ql:5,3-11)
+ERROR: Could not resolve module DataFlow (local.ql:6,3-11)
+ERROR: Could not resolve module DataFlow (local.ql:8,3-11)
+ERROR: Could not resolve module semmle.code.python.dataflow.DataFlow (local.ql:2,8-44)

python/ql/test/experimental/dataflow/local.ql

@@ -0,0 +1,10 @@
+import python
+import semmle.code.python.dataflow.DataFlow
+
+from
+  DataFlow::Node fromNode,
+  DataFlow::Node toNode
+where
+  DataFlow::localFlowStep(fromNode, toNode)
+select
+  fromNode, toNode

python/ql/test/experimental/dataflow/test.py

@@ -0,0 +1,8 @@
+a = 3
+b = a
+
+def f(x):
+  y = x + 2 # would expect flow to here from x
+  return y - 2 # would expect flow to here from y
+
+c = f(a)