EA-87708 Fixed: NPE: PyFunctionImpl.getWrappersFromStub

PY-19412 Fixed: Class method support becomes broken if method attribute is used

Check all next siblings stubs of PyTargetExpressionStub type in function modifier calculating and honour all nullable values

python/testData/inspections/PyArgumentListInspection/ReassignedViaClassMethodInAnotherModule/a.py

@@ -0,0 +1,7 @@
+class Spam(object):
+
+    def spam(cls):
+        pass
+
+    eggs = False
+    spam = classmethod(spam)

python/testData/inspections/PyArgumentListInspection/ReassignedViaClassMethodInAnotherModule/b.py

@@ -0,0 +1,3 @@
+from a import Spam
+
+Spam.spam()