UpDownBaseTests are severely leaking

[Youssef1313]

There is a severe memory leak in some UpDownBaseTests.

As shown in this trace, there are subscriptions to UserPreferenceChanged that are never unsubscribed.

One example is UpDownBase_OnHandleCreated_Invoke_CallsHandleCreated which manually calls OnHandleCreated (which subscribes to the event), but never calls OnHandleDestroyed.

Alternatively, might be worth try calling CreateHandle instead of OnHandleCreated, so that Dispose can see that a handle is created and then it can destroy properly.