Deprecate Graph.Exceptions.elementNotFound

As it sits right now, the standard elementNotFound exception is not used in the core code base, but we are validating that it is being thrown in the test suite by providers! The test is actually faulty because it is not asserting the message and just that it is a NoSuchElementException which is causing the problem. We should either deprecate this method and just validate NoSuchElementException or use it in full and force providers to do the same.

This has the potential to be a breaking change as it might break tests if providers aren't using that standard exception.