Python: Move json tests to be part of stdlib

This is better, since the modeling is also part of Stdlib.qll

Author: RasmusWL

python/ql/test/experimental/dataflow/tainttracking/defaultAdditionalTaintStep/test_json.py

@@ -0,0 +1,40 @@
+from io import StringIO
+import json
+
+def test():
+    print("\n# test")
+    ts = TAINTED_STRING
+
+    encoded = json.dumps(ts) # $ encodeOutput=json.dumps(..) encodeFormat=JSON encodeInput=ts
+
+    ensure_tainted(
+        encoded, # $ tainted
+        json.dumps(ts), # $ tainted encodeOutput=json.dumps(..) encodeFormat=JSON encodeInput=ts
+        json.dumps(obj=ts), # $ tainted encodeOutput=json.dumps(..) encodeFormat=JSON encodeInput=ts
+        json.loads(encoded), # $ tainted decodeOutput=json.loads(..) decodeFormat=JSON decodeInput=encoded
+        json.loads(s=encoded), # $ tainted decodeOutput=json.loads(..) decodeFormat=JSON decodeInput=encoded
+    )
+
+    # load/dump with file-like
+    tainted_filelike = StringIO()
+    json.dump(ts, tainted_filelike) # $ encodeFormat=JSON encodeInput=ts
+
+    tainted_filelike.seek(0)
+    ensure_tainted(
+        tainted_filelike, # $ tainted
+        json.load(tainted_filelike), # $ tainted decodeOutput=json.load(..) decodeFormat=JSON decodeInput=tainted_filelike
+    )
+
+    # load/dump with file-like using keyword-args
+    tainted_filelike = StringIO()
+    json.dump(obj=ts, fp=tainted_filelike) # $ encodeFormat=JSON encodeInput=ts
+
+    tainted_filelike.seek(0)
+    ensure_tainted(
+        tainted_filelike, # $ tainted
+        json.load(fp=tainted_filelike), # $ tainted decodeOutput=json.load(..) decodeFormat=JSON decodeInput=tainted_filelike
+    )
+
+
+# Make tests runable
+test()