Add "Py" prefix to AddImportQuickFixTest and several other quick fix tests

otherwise it's easy to overlook it especially considering that there is
also (confusingly) PyAddImportTest

python/testData/quickFixes/PyAddCallSuperQuickFixTest/oldStyle.py

@@ -0,0 +1,10 @@
+class A():
+    def __init__(self):
+        a = 1
+
+class C(A):
+    def <warning descr="Call to __init__ of super class is missed">__ini<caret>t__</warning>(self):
+        pass
+
+    def foo(self):
+        pass